Point of order, guys... Any Highway with a current U.S. designation ( U.S. 101, U.S. 97, U.S. 395 as examples ), receives Federal Highway Trust Fund dollars for at least part of its upkeep & improvements. Maybe not to the degree that Interstate Highways do, but certainly more than state roads do. When the Interstate Highways were being mapped out, it was determined that many areas & towns ( Eureka & Bishop, CA., Central Oregon & Nevada ), did not require a multiple - lane high speed highway, yet were still worthy of a Federal Highway. (Politics entered into the picture here.) As the Interstate Highway system took shape, many parallel U.S. Highways(U.S. 99, U.S. 66, U.S. 91), lost their Federal funding & reverted to State Highways. In more recent times, States have lobbied the Fed to convert State Highways to Interstate Highways, in order to obtain a greater share of FHTF money. Examples include the Nimitz, Long Beach, & Harbor Freeways in California.
Try this website for more info - [www.cahighways.org]