c. 1930's city of chicago vintage american single-sided automobile speed limit traffic sign. the surface exhibits an age old allover crazed finish. the sign is comprised of a heavy gauge die cut steel plate with rounded corners. the exact sign fabricator is not known. speed limit laws, which date to 1901, traditionally have been the responsibility of the states. before 1973, when congress responded to oil shortages by directing the us department of transportation to withhold highway funds from states that did not adopt a maximum speed limit of 55 mph, speed limits on rural interstates in most states ranged between 65 and 75 mph, with the majority of states setting rural interstate speed limits of 70 mph. in urban areas, most states maintained 55 mph speed limits before the national maximum speed limit was established. by march 1974, all states adopted the 55 mph national maximum speed limit. as concerns about fuel availability and costs faded, however, and speeds began to gradually climb on us highways, congress in 1987 allowed states to increase speed limits on rural interstates to 65 mph. measures 18 x 12 inches.