Due to its small size and number of commercial trucks based within its borders, it's not surprising that Washington, D.C. was the last American jurisdiction to introduce plates of this type. Apportioned plates are issued for use on commercial vehicles that travel across state lines. Registration fees are apportioned to jurisdictions in which the vehicle is operated based upon records of mileage travelled maintained by the owner.

The first District of Columbia apportioned plates have embossed characters that are painted black, whereas by 2009 they were being issued in the flat style with blue figures. Plates of this type are validated with a sticker affixed to the plate, not to the windshield.

Current Type Designation: T prefix

The first year of issue for this type is unknown. Because 1927-34 plates with only a T prefix were issued for use on private passenger cars, a TR prefix was used to identify trailer plates before 1935, when the type name TRAILER was first embossed.

The current trailer numbering sequence began with registration number T-101 issued in April 1974 when all existing 1973 (exp. 3-31-74) plates were replaced with 1974 (BICENTENNIAL) multi-year baseplates. By 2010 numbers were approaching 20000 (such as the examples pictured below), indicating that about 19,000 trailer plates were issued during a 37-year period, an average of about 500 plates per year or about two per DMV business day.

So few post-1974 examples of this type are known that little is known about which registration numbers appeared on the various baseplates issued since 1974. The lowest and highest numbers known on the vartiey of the 1991 (Celebrate & Discover) base with the slogan at the top are 10065 and 15017, respectively, and the lowest number on the current flat style is 15672. It's entirely possible that trailer plates were not made on every base variety utilized since 1974.