The term APPORTIONED on a license plate refers to an interstate vehicle, usually a truck or a tractor.   When a truck has APPORTIONED plates on it, it pays road taxes to all the states it travels through - in proportion to how much of the time the truck is actually in that state.   Thus, the tax fees are split up, or "apportioned", between the states where the truck travels.   This way, the truck does not have to carry a license plate from each state it goes through.   The only plate required is the APPORTIONED plate from the truck's home state.   Before these plates came along, trucks were required to have one license plate from each state it drove through - and sometimes this could be a lot of plates !! The IRP (International Registration Plan) was formed in 1973 to be an agreement between the participating jurisdictions which regulated the payment and apportionment of fees.   Learn about its history here.   Today, all of the lower 48 states - and most of the Canadian provinces - are members of the IRP.   They issue either APPORTIONED or PRORATE (PRP) plates for interstate or inter-province vehicles.   Alaska used to issue APPORTIONED plates, but it stopped in 1979.   Hawaii never has, and more than likely, never will.   A list of current jurisdictions participating in the IRP is below. Several states also previously issued APPORTIONED plates for trailers as well - but the last state which required apportioning of trailers (California), dropped the requirement in 2001.   Now, APPORTIONED trailer plates are being replaced by "Permanent" trailer plates in many states. APPORTIONED plates have been issued to trucks, tractors, trailers, buses, and even farm vehicles !! Commemorative plate from the IRP convention in 2008.  JURISDICTION ENTERED INTO IRP FIRST APPORTIONED PLATE  Texas April 1, 1974 1973  Missouri January 1, 1974 1974  Tennessee March 1, 1974 1974  Kentucky April 1, 1974 1975  Colorado January 1, 1975 1975  Alberta January 1, 1975 1976 (Sticker on PSV plate)  Minnesota January 1, 1975 1976  Nebraska January 1, 1975 1975  Oregon January 1, 1975 1975  South Dakota January 1, 1975 1976  Utah January 1, 1975 1976  Virginia March 1, 1975 1976  Mississippi November 1, 1975 1976  Idaho January 1, 1976 1976  Montana January 1, 1976 1977  Wyoming January 1, 1976 1975 base  Louisiana April 1, 1976 1975  Arkansas July 1, 1976 1977  Alaska c.1976 (withdrew 1979) 1976 (stickered 77,78,79)  Illinois January 1, 1977 1977  North Carolina January 1, 1977 1977  Iowa January 1, 1978 1978  Oklahoma January 1, 1978 1978  Wisconsin January 1, 1978 1978  Alabama October 1, 1980 1981  Arizona January 1, 1981 1980  Kansas January 1, 1981 1980  North Dakota January 1, 1981 1981  Pennsylvania June 1, 1983 1983  California January 1, 1985 1982  Michigan March 1, 1985 c.1985  Connecticut May 1, 1985 c.1987  South Carolina January 1, 1986 1986  West Virginia July 1, 1986 c.1985  Florida December 1, 1986 1987  Indiana March 1, 1987 1987  Washington January 1, 1988 1988  Maryland May 1, 1988 1989  Vermont May 1, 1988 1988  New York March 1, 1989 1989 (Liberty Base)  New Hampshire May 1, 1989 1989  New Mexico January 1, 1990 1990  Georgia January 1, 1991 1991  Ohio June 1, 1991 1992  Nevada January 1, 1992 1992  Maine July 1, 1993 1993  Saskatchewan October 1, 1993 "APPORTIONED" sticker c.1997  Massachusetts January 1, 1994 1994 ??  Delaware January 1, 1995 1995  British Columbia January 1, 1996 c.1990 ??  New Jersey April 1, 1996 June 1996 (12/96 sticker)  Rhode Island September 1, 1996 1998 ??  District of Columbia April 1, 1997 1999 ??  Manitoba March 1, 2001 "APPORTIONED" sticker c. 3/2001  New Brunswick April 1, 2001 still "PRP"  Newfoundland & Labrador April 1, 2001 2001  Nova Scotia April 1, 2001 2005  Ontario April 1, 2001 Interim "PRP" sticker 2001  Prince Edward Island April 1, 2001 still "PRP"  Quebec April 1, 2001 still "PRP" sticker  Hawaii Non-member  Northwest Territories Non-member  Nunavut Non-member  Yukon Non-member