Route 370 begins in St. Peters at a Y-interchange at I-70 exit 224 east of Mid Rivers Mall Drive and proceeds northeast.

It loops around Fountain Lakes Park and crosses Cole Creek before turning to a southeasterly direction.

It then passes north of St. Charles and interchanges with Route 94 at exit 7 before crossing the Missouri River.

The route ends in Bridgeton, forming another Y-interchange at exits 22A and 22B on I-270 west of Missouri Bottom Road.

It was built to replace the section of St. Charles Rock Road, then designated as Route 115, west of I-270.