Interstate 370 Missouri

I-370 Missouri


Missouri Route 370 is a 12 mile long freeway connecting I-270 with I-70 in the vicinity of St. Charles, northwest of St. Louis. Interstate 370 currently does not exist in Missouri. Although Route 370 is a freeway, it was constructed without Interstate funding. No official plans are in place to redesignate the state highway as an Interstate.1

Route 370 was considered as I-370, but it would only be approved by the American Association of State Highway and Transportation Officials (AASHTO) if it were designated as I-870.2,3 Missouri objected to this, because Interstate 870 was a designation that was supposedly being reserved for a bypass route in Columbia.4


Missouri Route 370 was originally planned as Missouri Route 115, but it was renumbered to be consistent with the numbering of I-70 and I-270. A brief chronology of the freeway:5

  • August 3, 1984 – Route 115 preliminary alignment adopted by the Missouri Highways and Transportation Commission for section from Interstate 270 to Route 94
  • 1985 – Highway 115 Northern Corridor Commission formed to promote the development of the new freeway
  • April 1987 – gasoline tax approved by voters; funds used for Route 370 extension from Route 94 to Interstate 70
  • December 1988 – Construction began with new interchange at Interstate 270
  • December 16, 1992 – Discovery Bridge and first leg of Route 370 opens ahead of schedule at a ribbon-cutting ceremony
  • 1997 – remaining section from St. Charles to St. Peters opens; old Route 115 bridge demolished

Route Information

  • East End – Bridgeton, MO

  • West End – St. Peters, MO

  • Mileage – 12.96

  • Cities – St. Peters, St. Charles, Bridgeton, Hazelwood

  • JunctionsI-70 I-270

Highway 370 Annual Average Daily Traffic (AADT)

Location Vehicles per day
Exits 1B to 2 46,337
Exits 2 to 5 51,979
Exits 5 to 7 51,421
Exits 7 to 9 58,267
Exits 9 to 11 52,288

 Photo Guides

East End I-270 – Bridgeton, Missouri

I-270 West at Route 370

I-270 west at Route 370 - Hazelwood, MO

Missouri Route 370 is a viable alternative from I-270 for Interstate 70 west to Wentzville and Kansas City via the Discovery Bridge between Bridgeton and St. Charles. 10/16/04

I-270 west at Route 370 - Hazelwood, MO

Three quarters of a mile ahead of Route 370 on Interstate 270 by the Hazelwood and Bridgeton city line. 10/16/04

I-270 west at Route 370 - Hazelwood, MO

Two lanes depart for Missouri Route 370 west at Exit 22B. 10/16/04

I-270 west at Route 370 - Hazelwood, MO

Entering the directional T interchange with Route 370 west to St. Charles from I-270 in Bridgeton. 10/16/04

West End I-70 – St. Peters, Missouri

I-70 West at Route 370

I-70 west at Route 370 - St. Peters, MO

Crossing into the city of St. Peters, I-70 advances one mile west to Exit 224 with Route 370 east. 10/16/04

I-70 west at Route 370 - St. Peters, MO

Route 370 arcs northeast from I-70 back into St. Charles en route to Elm Point and the Discovery Bridge across the Missouri River. 10/16/04

I-70 west at Route 370 - St. Peters, MO

A directional T interchange connects Interstate 70 and Missouri Route 370 at Exit 224. 10/16/04


  1. “They built it, and they came: Highway 370, Discovery Bridge have served many purposes.” Suburban Journals of Greater St. Louis (MO), December 12, 2006.
  2. Interstate 370 – (Scott Oglesby)
  3. Boor, Anthony “Re: MO S.R. 370 and The Boeing Company (was Re: I-180 now more useless than ever!).” Online posting. December 18, 2001. news misc.transport.road.
  4. Dowd, Brian “Re: I-64 st louis experience” Online posting. November 10, 2004. news misc.transport.road.
  5. Dowd, Brian. Personal email, May 25, 2004.
  6. Dowd, Brian. “Mo Highway notes” Personal email, November 22, 2004.

Page updated July 21, 2021.