Illinois Route 136 is an east–west road in northwestern Illinois. It runs from the Mark N. Norris Bridge over the Mississippi River, connecting to Iowa Highway 136 in Clinton, Iowa, east to U.S. Route 30 east of Fulton. This is a distance of 3.22 miles (5.18 km).

Illinois 136 is a two-lane surface road for its entire length. Route 136 begins at the Mark N. Norris Bridge which connects to Iowa Highway 136 in Clinton, Iowa. At the foot of the bridge is a signal-controlled intersection with 4th Street in Fulton, which is signed as the Lincoln Highway. Route 136 continues east along 14th Avenue, a residential street dotted by churches and businesses. On the eastern edge of Fulton, Route 136 intersects Illinois Route 84. The final 2 miles (3.2 km) of Route 136, which run along Fulton Road, are part of the Lincoln Highway and are signed as such. Route 136 ends at an intersection with U.S. Route 30.

SBI Route 136 originally ran from Illinois Route 1 to the village of Flat Rock in rural Crawford County, a distance of about 3,000 feet (914 m). In the meantime, the Lyons-Fulton Bridge was numbered U.S. 30 through 1957, and Alternate U.S. 30 through 1967. After 1967, the bridge and road to U.S. 30 were changed to Illinois Route 136. In 1975, the Lyons-Fulton Bridge closed and was replaced by the Mark N. Norris Bridge located a 1⁄2-mile (0.80 km) downstream. The spur to Flat Rock was left unnumbered.