A Pictorial History of Pennsylvania License Plates
Trailer Plates Dated 1914 to Present

Trailers

1914-1919 trailers
In Pennsylvania, trailers were first registered in 1914, and so there were two years of porcelain-coated trailer license plates issued before the state switched over to embossed plates. Trailer plates did not have the keystone attachment with the maker's number (today know as the VIN) on them like car and truck plates did. Instead, the state abbreviation "Penna", the four-digit year, and the word "Trailer" were stacked on the left side of the plate. Trailer plate serial numbers had a "T" prefix, and probably started from T1.

Beginning in 1916, trailer plates were embossed like all other Pennsylvania plate types, but the basic design of the plates were otherwise unchanged from the previous years' porcelain plates. In 1919, similar to other plate types, the state abbreviation, the year, and the "Trailer" plate type were relocated to the right side of the plate.

1920-1923 trailers
I've only seen one trailer plate from these years, and so I'm having to make some assumptions about the other years based on the one I have seen, plus various other 1920-1923 Pennsylvania non-passenger plates.

The one trailer plate I have seen was from 1922. It had the legend "Penna Trailer 1922" along the bottom of the plate, again had a "T" prefix, followed by a two-digit number. Despite the low serial number, the plate was 16 inches long, necessary for the bottom text to fit on the plate. With no text at top, the plate was standard 6 inch height.

Likely the same plate layout was used in 1921 and 1923 as well. I'm a bit less certain about the 1920 trailer plates, because although some non-passenger types had this layout in 1920, others did not. The one 1920 truck plate I've seen had the vehicle type at the top edge of the plate, while the state abbreviation and year were at the bottom; therefore, the plate was taller than 6 inches, and less than 16 inches wide since it had only a five digit serial.

1924-1929 trailers
During these years there was no legend to identify trailer plates, and beginning in 1924, truck plates began using a single "T" serial prefix, along with all the other letters from R to W, plus Y and Z. Therefore, trailer plates were now identified only with a double "TT" prefix.

I've only seen a very few examples of trailer plates from these years, but it would seem that, like truck plates, serial letters were the same size as the numbers from 1924 through 1926, and then since 1927, always noticeably smaller than serial numbers. It also appears that in some years and with some numbers of serial characters, a dash separator was used between the third and fourth characters from the right, while in other situations no dash was used. This was also the case with other plate types from the 1920s, but again, I haven't seen enough trailer plates to really nail down when the dash was used and when it wasn't.

1930 trailers
Even to someone familiar with old Pennsylvania license plates, 1930 trailer plates are easily mistaken for truck plates. Again, the plates bore no legend identifying the plate type. However, during 1930 only, trailer plates reverted back to the single "T" prefix used on trailer plates from 1914-1923. The "T" prefix indicated a truck plate during 1924-1929 as well as from 1931 through 1967.

1931-1933 trailers
Information about trailer plates for these years is scant and contraditory. I have not seen even a photo of a 1931-1933 Pennsylvania trailer plate to verify or refute any of the information I do have.

One source says that the 1930 trailer format, with a single "T" prefix followed by a number of up to four digits, continued through 1933. Another source says that the double TT prefix used during 1924-1929, followed by a either a four digit number or a number of up to four digits, was resumed. In neither case was a "trailer" legend embossed on the plate to identify the plate type, nor were there any other letters on the plate besides "T". Both formats are entirely possible since they were not used for passenger cars, trucks, or any other plate type of which I'm aware.

1934-1937 trailers
For 1934, and continuing to the present, trailer plates bore a legend that clearly identified them as such. During The 1934 and 1935 plates had the legend "Trailer" at the bottom edge, flanked by two embossed keystones, the four digit year running vertically down the left edge, and the state abbreviation "Penna" running vertically down the right. The serial was all numeric, with no prefix, and could be from one to four digits. The 1936 and 1937 plates were basically flip-flops of the 1934-1935 plates; they had the "Trailer" legend with the keystones along the top edge, and the positions of the year and state abbreviations were reversed. By 1937, if not sooner, over 9,999 trailers were registered, and in order to keep the serial number at four characters, a variable letter was introduced in serial position 1. I can't say whether these alpha-prefix trailer plates could have fewer than four serial characters or whether the letter could be followed by one or more zeroes.

1938-1957 trailers
Starting in 1938, trailer plates bore the state map outline that was introduced on passenger plates in 1937. The legend was yy#Trailer#Pa with # indicating embossed keystones. During the years when passenger car plates came in two different sizes based on the number of serial digits, trailer plates apparently were all made in the longer size due to the length of the plate type legend.

Serial number formats were now a minimum of four digits, and up to five digits, with lead zeros used on four character plates when necessary. It appears that formats were employed in this sequence: 0000, x000, 0x00, 00x0, 000x, 00000, although not all formats were used in the early years. The first year I've seen a five digit trailer plate is 1951, though of course this format might have made its debut earlier than that. For 1957, all trailer plates were given six digit, all numeric serials, apparently starting at 100001. These did not have any dash separator.

It seems unimaginable to us now, but during all of these years, passenger car, motorcycle, trailer, and farm tractor plates all used at least some of the same serial formats, and therefore their serial numbers duplicated each other. For example, there would have been four different plates in use at any given time with plate number A101 - one for each of the vehicle type listed above. I suppose the thinking was that these vehicle types were different-looking enough that there should be no confusion.

Like all other plate types, the registration period was changed from the calendar year to end on March 31 of the year following the year indicated on the plate, beginning with the 1941 plate. Starting with this plate, the actual expiration date was added in very small characters along the top edge of the plate. Along with truck plates, the expiration date of trailer plates was changed again effective with the 1953 plates to be May 31 of the year following the year indicated on the plate. Meanwhile, passenger car plates continued with March 31 expirations.

1958-1967 trailers
Like truck plates, multi-year trailer base plates were issued in 1958 and again in 1964. Both of these base plates were yellow on blue, causing the color scheme to be opposite that of passenger cars from 1965 thorough 1967. Continuing the serial format introduced in 1957, all trailer plates had a six digit, all numeric serial number, apparently starting at 100-001. A small keystone separator was introduced, located between the third and fourth serial characters. Once again, this format was the same as, and serial numbers overlapped with, both passenger car and farm tractor plates.

Stamped along the top of these plates were "Pa Trailer 58" and "Pa Trailer 64", respectively. In years that base plates weren't issued, renewal stickers were applied in the upper left corner of the plate. The stickers were the same colors as passenger car stickers from 1959 to 1963, and the same colors as truck stickers from 1965 to 1967. The exact expiration date was no longer indicated, but as far as I know, continued to be May 31 of the year following the year of the plate or sticker. For example, a trailer plate with a 1963 sticker was actually valid until May 31, 1964.

1968-1971 trailers
The multi-year trailer base plates issued from 1968 to 1971 were blue on yellow, matching the 1965-1970 passenger plate colors, and bore the legend "Trailer" along the top edge and the fully-spelled state name along the bottom edge. The serial format was changed to Tx-00000, and this format was now unique to trailers. Well, almost; farm tractor plates got format TR-00000, but trailer plates never got anywhere close to the TR series. The small keystone separator continued to be used, now between the serial letters and numbers. Like other non-passenger plate types, trailer plates again had a border in the shape of the state, sort of. The legend at the top necessitated redrawing the northern border of the state well into New York. These plates had a real sticker box with an embossed border in the lower left corner. Early issues of this base plate had a lightly debosssed "68" in the sticker box. The plate was used without stickers during 1968; stickers were applied during 1969-1971. Trailer sticker colors again were the same as truck stickers. I presume that expiration dates continued to be the May 31 of the year following the year indicated on the plate or sticker, so these plates were actually used through May 31, 1972.

1972-1977 trailers
These plates were introduced one year after and continued to be issued one year after the corresponding Bicentennial passenger plates. 1972 to 1977 trailer plates were yellow on blue, again with "Trailer" at the top and the state at the bottom. The state map outline used continuously since 1938, which had become grotesquely distorted in 1968, was put out of its misery. Serial format Tx-00000 was again used, still with a small keystone serial separator. Again, format TR-00000 was used for farm tractors, but trailer plates never got that high. Sticker wells were in both upper corners. Early issues had a lightly etched "72" in the left sticker well. The plate was used without stickers in 1972; stickers were applied 1973-1977. Again, sticker colors were the same as were used for truck plate stickers. Most likely, expiration dates continued to be May 31 of the following year, so this base plate was used through May 31, 1978.

1978-2000 (yellow base) trailers
These blue-on-reflective-yellow plates were introduced about one year after the corresponding Keystone State passenger plates, starting in 1978 to about 1984 or so, or possibly even a year or two beyond 1984. These plates could then be renewed through 2000 expiration dates. The state name was now stamped at the top, between sticker wells located in the upper corners, and the "Trailer" legend was moved to the bottom.

The trailer plate serial format was again Tx-00000, now with a dash separator rather than a keystone, and trailer plates got up to the TK series on this base. There were now two other plate types with similar serial formats; tractor plates again had format TR-00000, but now taxi plates were introduced on this base; their format was TX-00000, with the second letter an actual "X".

These trailer plates were undated and were used without stickers during the first year of issuance, likely through May 31, 1979. Red on white 1979 stickers were valid apparently through May 31, 1980, and then the state converted to staggered registration periods. As far as I know, trailer plates were converted to staggered registrations just like passenger car plates were. If so, then upon expiration of the 1979 sticker in March 1980, trailers were assiged a new month that fell in the range of September 1980 to August 1981. Single stickers bearing both the month and year of expiration have been used ever since.

1985-2002 (blue base) trailers
Yellow on blue Pennsylvania plates were issued from about late 1984 to June 2000; however, not all plate types began at the same time, and I don't know exactly when yellow on blue trailer plates were first issued or the previous blue on yellow plates were last issued. The switch occurred sometime in the mid-1980s. The yellow on blue plates could be renewed through June 2002. These blue plates had a single sticker well in the lower left corner. Serial numbers continued in the same formats from the previous base. There were two types of trailer plates issued on this base, although the second wasn't introduced until a few years before the end of this base's life.

• Regular trailers - The serial format continued to be Tx-00000, and picked up where the previous base left off, in the TL series. Early plates in the TL series continued with the previous base's placement of the state name and plate type, with "Pennsylvania" at the top and "Trailer" at the bottom. However, somewhere during the TL series, the locations of these elements were switched to be consistent with other plate types on this base.

Once the state name was moved to the bottom and "Trailer" to the top, these plates were strikingly similar in appearance to the 1972-1977 trailer plates. There are several ways to distinguish them, however, even if the plate does not have an expiration sticker. The 1970s trailer plates had two sticker wells in the upper corners, while the 1985-2002 trailer plates had a single sticker well in the lower left corner. The earlier plates had a keystone separator, while the later plates had a dash separator. And, I haven't come across a blue 1970s trailer plate past the TJ series, while the blue 1980s trailer plates began at the TL series.

Prefixes TR and TX were skipped for trailer plates, since they had been used for farm tractor and taxi plates, respectively. Plate TZ-99999 was issued sometime in the early 1990s, late 1993 according to one source, and the trailer serial format used since 1968 was exhausted. Then, a new serial format Xx-00000 was begun, with the first character always an "X" and the second letter variable. As far as I know, lead zeroes began to be used on these X-series trailer plates for the first time since 1956. Trailer plates got up into at least the XH series, possibly the XJ series, before this base was discontinued.

• Permanent trailers - According to one source, this plate type was introduced in 1997. Serial format was PT-00000 on this base, and the legend "Perm-Trailer" was embossed at the top of the plate. The normal debossed sticker well was put in the lower left corner, but no stickers were used on these plates. Despite the "permanent" designantion, these blue plates were apparently replaced with tri-color plates during the 2000-2002 general reissue.

2000-present (tri-color band base) trailers
Tri-color plates with blue and yellow bands that fade to white were first introduced in 1999 with 2000 expirations. Tri-color plates with solid navy and yellow bands were introduced for regular trailers beginning in 2005 as existing stock of the earlier fade plates were used up. The original tri-color fade plate style continues to be used and renewed.

Both styles of tri-color plates are blue at the top, white in the middle, and yellow at the bottom, with embossed serial characters painted dark blue. The state name is screened on in the blue band in white captital letters. There's a single sticker well in the upper left corner.

• Regular trailers - Embossed "Trailer" along the bottom. Fade-style plates continued with the previous base's Xx-00000 serial format and picked up numerically where the previous plates ended, starting with the XK series. When serial XZ-99999 was reached in 2004, a new format Xxx-0000 was introduced, starting at XBA-0000. (Pennsylvania has tended to avoid vowels in the middle letter position in recent years.) Fade plates also had a dash separator between the letters and numbers. Solid band regular trailer plates were introduced in 2005 beginning with serial XCA-0000. These plates have a keystone separator.

• Permanent trailers - "Perm-Trailer" is embossed at the bottom, serial format is PT-0000x. Serial numbers advance before the alpha suffix. These plates are correctly used without a sticker indicating an expiration date, since they're, well, permanent. The ones I've seen do have the sticker well in the upper left corner nevertheless. Fade band plates were issued with suffix letters "A" through "K" and have a dash separator; solid band plates continued with suffix letters beginning with "L" and use a keystone separator. The solid band plates first made their debut in approximately early 2007.