Interstate 580, the longest spur route of I-80 in California, runs 81 miles from U.S. Route 101 at San Rafael in Marin County to Interstate 5 in Tracy in San Joaquin Valley, passing through Oakland and the Altamont Pass in the process. It has a crossing of the San Francisco Bay via the Richmond-San Rafael Bridge. I-580's 5-mile overlap with I-80 between Albany and the MacArthur Maze on the west edge of Oakland in Alameda County is not federally recognized, thus technically making it a discontinuous two-piece highway.