It spans a total of 36.6 miles (58.9 km)[1] as a two lane, undivided road.

In 1972, LA 20 was routed off of Jackson Street in downtown Thibodaux and onto parallel Canal Boulevard, a four-lane, largely residential thoroughfare.

[2] The extension of Canal Boulevard north of Bayou Lafourche was to be opened soon, bypassing St. Patrick Street.

[2][3] The route change was opposed by Thibodaux's mayor, Warren Harang, and the Louisiana Department of Highways agreed to keep truck traffic routed via Jackson Street,[2] which was retained as LA 20 Spur.

[7][8] The ferry service was replaced by the newly opened Gramercy Bridge (or Veterans Memorial Bridge) in May 1995,[9] and LA 20 was truncated to its present terminus in Vacherie two years later.