Route 135 is a 29.53-mile-long (47.52 km) east-west state highway in eastern Massachusetts. The western terminus is at U.S. Route 20 in Northborough and the eastern terminus is at I-95 and Route 128 in Dedham. The first 13 miles (21 km) of the Boston Marathon, from Hopkinton to Wellesley, follow Route 135.