Missouri State Route 340 runs east-west in the western areas of St. Louis County. In Chesterfield it turns into a north-south highway. MO St Rt 340 passes through the following towns in St. Louis County. Ellisville
Clarkson Valley Ballwin
Chesterfield
Creve Coeur
Olivette University City MO St Rt 340 is not multi-plexed in St. Louis County. MO St Rt 340 intersects the following highways in St. Louis County. Missouri State Route 100, at Ellisville.
A BGS on SB I-170. A BGS on NB I-170. A BGS on SB I-170. A BGS on NB U.S. Rt. 67. EB MO St Rt 340 in Creve Coeur. A BGS on SB I-270. A BGS on NB I-270. A BGS on NB I-270. WB MO St Rt 340 east of Fee Fee Road. WB MO St Rt 340 west of Fee Fee Road. WB MO St Rt 340 at MO St Rt 141. A BGS on NB MO St Rt 141. A BGS on SB MO St Rt 141. A BGS on WB I-64/U.S. Rt. 40; NB U.S. Rt. 61. A BGS on WB I-64/U.S. Rt. 40; NB U.S. Rt. 61. A BGS on EB I-64/U.S. Rt. 40; SB U.S. Rt. 61. SB MO St Rt 340 at Baxter Road. SB MO St Rt 340 at Country Ridge Drive. A junction marker on WB MO St Rt 100. The southern end of MO St Rt 340. The southern end marker.
