Route 100, also named Manchester Road through St. Louis County and Manchester Avenue and Chouteau Avenue through St. Louis City, is a state highway in the U.S. state of Missouri.

The highway passes through New Haven, in Franklin County, 14 miles (23 km)[2] later.

Route 100 crosses over Interstate 44 two times, with an interchange providing access to the freeway.

Northeast of Gray Summit, Route 100 crosses into St. Louis County, entering the city limits of Wildwood at the same time.

From here all the way into St. Louis, the highway also carries the local name Manchester Road.

Route 100 then passes through the smaller suburbs of Warson Woods, Glendale, Rock Hill, Brentwood, and Maplewood.