When Tulsa businessman Cyrus Avery helped route the new U.S. Highway 66 through Oklahoma in the 1920s, he and his fellow promoters sold it to the country as the “Main Street of America.” What grew along Route 66 and its sister highways was a commercial architecture unlike anything that came before, including whale-shaped car washes, monumental drive-in theaters, and Will Rogers-themed motor courts. The Roads They Are a-Changin’: Oklahoma and American Car Culture gathers photographs made by…