I-270

About I-270

Also known as Outerbelt, Washington National Pike.

Interstate 270 is a three-digit auxiliary route of Interstate 70, with an even prefix digit marking it as a loop or bypass. The number is reused in several states. In the Washington, D.C. area, Interstate 270 is a heavily traveled spur of about thirty-five miles running from the Capital Beltway near Bethesda, Maryland, northwest through Montgomery County to Interstate 70 at Frederick, serving as a major commuter corridor.

In Ohio, Interstate 270 is a full beltway of about fifty-five miles encircling Columbus, locally called the Outerbelt. In Missouri and Illinois, Interstate 270 forms a large part of the outer belt around Greater St. Louis, crossing the Mississippi and Missouri rivers and running roughly fifty miles between junctions with Interstate 55. In Colorado, Interstate 270 is a short route of about seven miles in northeastern metropolitan Denver connecting Interstate 70 with Interstate 25 and U.S. 36 toward Boulder.

Across these states the number serves either as a metropolitan beltway or as a major connector spur, consistent with its even prefix digit.

History

The Maryland route grew into one of the busiest commuter corridors in the region as Montgomery County developed, and has been repeatedly widened. The Columbus Outerbelt and the St. Louis outer belt were built through the 1960s and 1970s to ring their metropolitan areas. The Colorado route provides a short but heavily used link in northeastern Denver.

Major cities and places

Notable features

• Mississippi River and Missouri River crossings on the St. Louis route

Did you know

• The Maryland route is a major commuter corridor from the Capital Beltway to Frederick.
• The Ohio route is the full Columbus beltway known as the Outerbelt.
• The St. Louis route crosses both the Mississippi and Missouri rivers.
• The even prefix digit marks each instance as a loop or connector.