Interstate 370 Missouri

I-370 Missouri
East End
West End


Missouri 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 Missouri 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

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

  • August 3, 1984 – Missouri 115 preliminary alignment adopted by the Missouri Highways and Transportation Commission for section from Interstate 270 to Missouri 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 Missouri 370 extension from Missouri 94 to Interstate 70
  • December 1988 – Construction began with new interchange at Interstate 270
  • December 16, 1992 – Discovery Bridge and first leg of Missouri 370 opens ahead of schedule at a ribbon-cutting ceremony
  • 1997 – remaining section from St. Charles to St. Peters opens; old Missouri 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

Highway Guides

East End I-270 – Bridgeton, Missouri

Perspective from Interstate 270 west
Missouri 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. Photo taken 10/16/04.
Three quarters of a mile ahead of Missouri 370 on Interstate 270 by the Hazelwood and Bridgeton city line. Photo taken 10/16/04.
Two lanes depart for Missouri 370 west from Exit 22B. Photo taken 10/16/04.
Entering the directional T interchange with Highway 370 west to St. Charles from I-270 in Bridgeton. Photo taken 10/16/04.

West End I-70 – St. Peters, Missouri

Perspective from Interstate 70 west
Crossing into the city of St. Peters, I-70 approaches Exit 224 with Highway 370 east. Photo taken 10/16/04.
Highway 370 arcs northeast from I-70 back into St. Charles en route to Elm Point and the Discovery Bridge across the Missouri River. Photo taken 10/16/04.
A directional T interchange connects Interstate 70 and Missouri 370 at Exit 224. Photo taken 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 February 1, 2019.