Interstate 170

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Interstate 170 marker

Interstate 170

Inner Belt Expressway
I-170 highlighted in red
Route information
Auxiliary route of I-70
Maintained by MoDOT
Length11.17 mi[1] (17.98 km)
Existed1956[citation needed]–present
Major junctions
South end I-64 / US 40 in Richmond Heights
Major intersections I-70 in Berkeley
North end I-270 in Hazelwood
CountryUnited States
CountiesSt. Louis
Highway system
US 169 Route 171

Interstate 170 (I-170), also known as the Inner Belt Expressway, is an 11.17-mile (17.98 km) north–south auxiliary Interstate Highway in Greater St. Louis, Missouri. I-170 connects to I-270 at its northern terminus and I-64 at its southern terminus. I-170 crosses its parent, I-70, near St. Louis Lambert International Airport.

Route description[edit]


I-170 was originally intended to provide an inner beltway within I-270 through St. Louis County extending to I-55 in the southern part of the county, commonly called South County;[2] however, the portion of the route south of I-64/US Route 40 (US 40) was canceled due to local opposition. The portion of MetroLink's Cross County Extension south of I-64 runs roughly along the proposed alignment.[3]

The southern portion of I-170 was built using St. Louis County funds in the 1960s through a shallow valley. It was signed as Route 725.

Recent construction[edit]

The southern two interchanges on I-170 (at I-64/US 40 and Galleria Parkway) were reconstructed as part of the first phase of the New I-64 project. Most notably, the new interchange includes direct access to I-170 from eastbound I-64; however, access to Galleria Parkway from northbound I-170 was eliminated. Eager Road access to and from I-170 was also revised in the New I-64 project.[4]

Southern extension[edit]

Because I-170 terminates at I-64/US 40, a direct access from I-170 and I-64 (US 40) to I-55, I-270, and I-44 are lacked. Also, towns such as Richmond Heights, Brentwood, Maplewood, and Marlbourough lack access to the Interstates, St. Louis Lambert International Airport, South County, and to each other. Because of this, commuters either have to take indirect surface streets as bypasses, such as Hanley Road or River Des Peres Boulevard, which would result in a much higher mileage and time due to traffic signals and a longer route. This also results in higher traffic in residential streets and towns such as Shrewsbury.[5] Proposals had been made to solve this problem, such as a new freeway for faster commute or "South County Connector" to connect Richmond Heights to South County, but these proposals had been postponed due to lack of funding.[6]

Exit list[edit]

The entire route is in St. Louis County.

Richmond Heights0.000.001 I-64 / US 40 / Lewis and Clark Trail – Wentzville, St. LouisSigned as exits 1A (east) and 1B (west)
0.4380.7051CBrentwood Boulevard north / Eager RoadSouthbound exit and northbound entrance
Clayton0.8091.3021DBrentwood Boulevard southSouthbound exit and northbound entrance (via Galleria Parkway)
1.1701.8831EForest Park Parkway eastWestern terminus of the Forest Park Parkway
Ladue1.6112.5931FLadue Road
University City2.3743.8212Delmar Boulevard
Olivette3.3365.3693 Route 340 (Olive Boulevard)
Overland4.3256.9604 Route D (Page Avenue)
St. John5.8659.4395 Route 180 (St. Charles Rock Road)
Bel-Ridge7.02711.3096 Route 115 (Natural Bridge Road) – Cargo CityAccess to the University of Missouri-St. Louis
Berkeley7.65412.3187 I-70 – St. Louis, Kansas CitySigned as exit 7A (east) and 7B (west); exit 235
7.77112.5067C Lambert–St. Louis International AirportSouthbound exit is via exit 7B
8.57713.8038Scudder Road / North Hanley RoadNo northbound entrance
9.16714.7539AAirport Road – Cargo City
9.23614.8649BBoeingNorthbound exit and southbound entrance
9.78015.7399CNorth Hanley RoadNorthbound exit and southbound entrance
10 I-270 – Kansas City, ChicagoSigned as exits 10A (west) and 10B (east)
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. ^ Starks, Edward (January 27, 2022). "Table 2: Auxiliary Routes of the Dwight D. Eisenhower National System of Interstate and Defense Highways". FHWA Route Log and Finder List. Federal Highway Administration. Retrieved February 22, 2023.
  2. ^ Sutin, Phil; Hopgood, Mei-Ling (January 9, 1997). "Hundreds of Homes Face Razing for New Highway". St. Louis Post-Dispatch.
  3. ^ Sutin, Phil (March 14, 1997). "Westfall Sours On Extension of Interstate 170". St. Louis Post-Dispatch.
  4. ^ "Project Overview". The New I-64. Missouri Department of Transportation. Archived from the original on May 4, 2007. Retrieved May 28, 2007.
  5. ^ Leiser, Ken. "Linking South County, Clayton studied". St. Louis Post-Dispatch. Retrieved January 19, 2018.
  6. ^ "South County Connector: 1st Phase of 170 South Extension?". May 14, 2013. Retrieved January 14, 2018.
  7. ^ Missouri Department of Transportation (March 18, 2015). MoDOT HPMAPS (Map). Missouri Department of Transportation. Retrieved March 18, 2015.

External links[edit]

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