or Puerto Rico?
The Hxx Interstates were approved by AASHTO when Hawaii became a state in 1959 to allow Hawaii to have Interstates (see http://www.fhwa.dot.gov/infrastructure/hawaii.htm and http://www.hawaiihighways.com/FAQs-page4.htm#why-Interstates ). Even though Alaska and Hawaii do not connect directly to other states, their highways fall into the same system as those in the other 48 states, so while “Interstate” can’t be literal, the name is there for consistency. Alaska and Puerto Rico officially have Axx and PRxx routes, respectively, but these are unsigned and, in Alaska’s case at least, generally not up to Interstate standards. In 1959, when Alaska became a state, they asked for funding for fully standard Interstates on the current corridors plus others, including one to Nome. This was rejected. In 1981, FHWA added current routes A1-A4 to the Interstate system as 2 lane rural arterials. The only Alaska Interstate routes that have been upgraded to freeway are AK 1 (A1) east of downtown Anchora
