Interstate 270 Maryland
Overview
Interstate 270 in Maryland is a regional connector between the Capital Beltway (I-495) and I-70 at Frederick. A heavily traveled commuter route, I-270 joins Washington, D.C. with points west to Hagerstown and Cumberland and north into Pennsylvania.
Just north of the Capital Beltway, I-270 splits into two branches. The main line angles east to link with I-495 by Chevy Chase. Interstate 270 Spur drops south to join I-270 with I-495 ahead of Cabin John and the American Legion Memorial Bridge across the Potomac River.
North from the merge of I-270 and I-270 Spur, the freeway expands with four overall roadways. The Local / Express configuration extends north to Gaithersburg and MD 117 (Clopper Road) at Exit 10.
History
The freeway for Interstate 270 was dually signed with U.S. 240, an intrastate route from Frederick, Maryland to Washington, DC. Interstate 70S was established along the route in 1956 and I-270 subsequently applied to what is now I-270 Spur. I-70 east to Baltimore was designated Interstate 70N.
U.S. 240 was decommissioned in 1972. The split route for I-70 was eliminated the following year, adhering to the AASHTO mandate to renumber all suffixes routes within the Interstate Highway System. I-70N became I-70 and I-70S was renumbered as I-270. I-270 Spur was created in place of the short I-270 on the west leg connecting with the Capital Beltway.

I-270 along I-270 Spur and U.S. 240 extending south from I-70S along MD 355 (Rockville Pike) – 1968 Maryland Official Map
$27 million in roadwork improved Interstate 270 at MD 187 (Old Georgetown Road) and Rockledge Drive east of I-270 Spur. Work rebuilt the diamond interchange and widened the MD 187 overpass to ten lanes. The project also improved access to Rock Springs Industrial Park with two new ramps from I-270. Despite inclement weather, construction wrapped up nine months ahead of schedule on November 4, 2003.1
Route Information
North End – Frederick, MD
South End – Bethesda, MD
Mileage – 34.40
Cities – Rockville, Gaithersburg, Frederick
- Junctions –
Source: December 31, 2018 Interstate Route Log and Finders List
I-270 Annual Average Daily Traffic (AADT)
I-270 Spur Annual Average Daily Traffic (AADT)
Location | Vehicles per day |
---|---|
I-495 to Exit 1 | 130,730 |
Exit 1 to I-270 | 131,292 |
Interstate 70S defaulted onto U.S. 15 north in Frederick prior to the 1960s completion of the freeway west from Frederick to Hagerstown.

Button copy signs preceding the split of I-70/270 eastbound previously referenced Interstate 70S. 02/18/94
Highway Guides
North End
– Frederick, Maryland
North at
East at
West at
West at
South at

Southbound on Interstate 270 at the split with I-270 Spur. This is the lone reference on guide signs for the spur route. Photo by Jeff Royston (06/10/06).
North at
Sources:
- “State Highway Administration Celebrates Opening of I-270/MD 187 (Old Georgetown Road)/Rockledge Drive Interchange in Montgomery County.” Maryland Department of Transportation (MDOT), news release. November 4, 2003.
Page updated December 11, 2020.