Interstate 270 Maryland


Interstate 270 in Maryland is a major connector route between Interstate 70 in Frederick and Interstate 495 (Capital Beltway). As the main connector between the Capital and transcontinental Interstate 70, Interstate 270 provides access to points west out of Washington D.C. At the beltway, I-270 splits into the main route and a spur route. Interstate 270 Spur is not generally signed as such, however, and it is referenced by the destination routes it serves.

Interstate 270 includes an express/local roadway configuration between the Interstate 270/Spur Interstate 270 merge and Maryland 117/Clopper Road (Exit 10) at Gaithersburg.


Prior to 1973, Interstate 270 was designated as Interstate 70S, with current Spur I-270 carrying Interstate 270 signage. Interstate 70 was signed as Interstate 70N at this time. The split route definition was eliminated when the AASHTO mandate on banning suffixed routes took effect.

The unconstructed leg of Interstate 70S from the Capital Beltway southeast into Washington was formally eliminated from the Interstate System along with the unbuilt I-95 through D.C. per AASHTO on November 15, 1975.

This map inset from the 1968 Maryland Official Map shows the original routing of Interstate 270 during the era when modern Interstate 270 was signed as Interstate 70S. What is now Spur I-270 was then known as Interstate 270. Note the routing of U.S. 240, which does not exist today (along the Maryland 355 alignment).

Roadwork improved Interstate 270 at Maryland 187 (Old Georgetown Road) and Rockledge Drive east of I-270 Spur. The $27 million project rebuilt the diamond interchange and widened the Maryland 187 overpass to ten lanes. The project improved access to Rock Springs Industrial Park with two new ramps from I-270. Despite inclement weather, the project opened nine months ahead of schedule on November 4, 2003.1

Highway Guides

Southern Terminus - Interstate 495 - near Bethesda, Maryland
Perspective from Interstate 270 south
Southbound Interstate 270 splits, with the left lanes providing high occupancy vehicles direct access to Interstate 495/Capital Beltway, and the right lanes splitting into Spur Interstate 270 south to Interstate 495/Capital Beltway south and Interstate 270 southeast to Interstate 495/Capital Beltway east. Photo taken by Jeff Royston (06/10/06).
Perspective from Interstate 495 west
Traveling west on the Capital Beltway/Interstate 495 (Outer Loop), the first appearance of Interstate 270 is on this mileage sign (three miles), just prior to the Maryland 185/Connecticut interchange (Exit 33) and Maryland 355/Wisconsin Avenue (Exit 34). Photo taken 07/12/05.
After Exit 33, Maryland 185, the Capital Beltway/Interstate 495 westbound approaching Exits 34 and 35 for Maryland 355 and Interstate 270 north. Maryland 355, otherwise known as Wisconsin Avenue, represents the former routing of U.S. 240, the predecessor to Interstate 70S and Interstate 270. Photo taken 07/12/05.
Exits 34 and 35 are adjacent to each other, both serving the Rockville and Gaithersburg communities. Maryland 355 also serves Bethesda, Washington, and the National Naval Medical Center. Interstate 270 will begin in one half mile. Photo taken 07/12/05.
Westbound Interstate 495/Capital Beltway reaches Exit 34, Maryland 355/Wisconsin Avenue. The next exit is the connection to northbound Interstate 270 at Exit 35. Photo taken 07/12/05.
Interstate 495 maintains three westbound lanes through the Exit 35 interchange with Interstate 270. There is no direct access to Interstate 270 northbound from Interstate 495 eastbound nor is there access to Interstate 495 west from Interstate 270 southbound at this location. Those traffic movements are handled by Spur Interstate 270 at Exit 38. Photos taken 07/12/05 and 08/04/00.
Interstate 270 westbound begins as Interstate 495 continues westward toward Northern Virginia. The next interchange for both freeways involves Maryland 187/Old Georgetown Road. Interstate 270 merges with Spur Interstate 270 in two miles. Photo taken 07/12/05.
Northern Terminus - Interstate 70 and U.S. 40 - Frederick, Maryland
Perspective from Interstate 70 east
Interstate 70/270 button copy signage at the split on Interstate 70 east. An imprint of a larger shield for Interstate 70S was faintly visible behind the Interstate 270 shield. However, this signage has since been replaced. Vidcap taken 02/18/94.
Eastbound Interstate 70 reaches Exit 52B, U.S. 15 north to Gettysburg. The next exit is the connection to southbound Interstate 270 to Washington, D.C. Photo taken by Jeff Royston (06/10/06).
This diagrammatic overhead sign shows how Interstate 70 and Interstate 270 will split in Frederick. The left two lanes continue east on Interstate 70 to Baltimore, while the right two lanes connect to southbound Interstate 270. Photos taken by Jeff Royston (06/10/06).
Perspective from U.S. 15 south/U.S. 40 east
Southbound on U.S. 15 and Eastbound on U.S. 40 in the city of Frederick approaching the northern beginning of Interstate 270. The two U.S. routes split, with U.S. 40 continuing (unsigned on this guide-sign) to Interstate 70/270, while U.S. 15 departs to the southwest for the westbound beginning of U.S. 340. Photo taken 10/01.
To connect directly between U.S. 15 and Interstate 270, one must take U.S. 40 for a short duration. As shown in this photo, traffic for U.S. 15 headed to Virginia must exit before the transition to Interstate 270. This exit also marks the northern end of U.S. 340, and U.S. 15 becomes its own independent freeway. U.S. 40 continues southeastward to a direct transition to Interstate 270 east. Photo taken 10/01.
Interstate 70/270 sign bridge from U.S. 40 Eastbound leaving Frederick. Although not well-signed, U.S. 40 follows Eastbound Interstate 70. Straight ahead is Interstate 270. Photo taken 10/01.
Southbound begin of Interstate 270 at the ramp for Interstate 70 East, as one leaves U.S. 40 from Frederick. This area is under construction to increase capacity for Interstate 70, Interstate 270, U.S. 40, and U.S. 15-340. This marks the southbound beginning of Interstate 270. Photo taken 10/01.
U.S. 40 appears on this Interstate 70 east gore point sign for the departure of the US route from Interstate 270. Downtown Washington, D.C. sits just 40 miles from this location via Interstate 270 (and Maryland 355). Photo taken by Tim Reichard (08/25/02).
Perspective from Interstate 70/U.S. 40 west
Interstate 70/U.S. 40 westbound approaching the city of Frederick. The upcoming exits panel on the left displays the next three off-ramps, all to limited-access highways. Meanwhile Exit 54 for Maryland 355/Market Street will depart in less than one mile. The state highway parallels Interstate 270 southward to Washington, D.C., and represents the original routing of U.S. 240. Photo taken by Tim Reichard (08/25/02).
Interstate 270 ends at Exit 53 of Interstate 70. The freeway itself however, continues northward as U.S. 40 to the Frederick Freeway/U.S. 15, near downtown. This westbound Interstate 70 photograph shows U.S. 40 leaving northward to meet U.S. 15. The next off-ramp, Exit 35A is for the southbound beginning of Interstate 270. Photo taken by Tim Reichard (08/25/02).
As U.S. 40 westbound overtakes the Interstate 270 mainline, an end Interstate 270 shield is posted. This is the view taken from the Westbound Interstate 70 ramp that carries U.S. 40 into downtown Frederick. Photo taken by Tim Reichard (08/25/02).
Spur Interstate 270 - Southern Terminus
Perspective from Interstate 495 north
Just after crossing the Potomac River from Virginia into Maryland, Interstate 495 sees its first Old Line State interchange with the Clara Barton Parkway at Exit 41. Also posted at this interchange is an upcoming Interstate junctions sign panel with the first indication of the pending split of Spur Interstate 270 from the Capital Beltway. Photo taken by Tim Reichard (02/08/03).
Nondescript overheads for Interstate 270 and 495 advise motorists of the impending split between the two freeways. The Beltway is four lanes wide at this point but will expand as it progress northward. Photo taken 10/14/01.
The dimness of winter sets in on the same set of Interstate 270 and 495 overheads Pictured above. In the background is a diagrammatic sign for Exit 38. Photo taken by Tim Reichard (02/08/03).
The Capital Beltway northbound widens to six lanes in anticipation of the split with Spur Interstate 270. The left-hand lane however, is allocated for HOV-2 traffic. Rather than indicate that Exit 38 is for Spur Interstate 270, the guide signage omits spur and just displays Interstate 270 shields. Photo taken 10/14/01.
Wintertime perspective of the Interstate 270/495 sign bridge Pictured in the above photograph. There are no Spur Interstate 270 signs or shields posted on Interstate 495 or on Interstate 270 itself. The only mentioning of the spur designation is on the mileposts of the highway itself. Photo taken by Tim Reichard (02/08/03).
Spur Interstate 270 begins as Interstate 495 turns from a northerly orientation to an easterly one. These extra large shield based signs saw installation with the most recent resigning of the Capital Beltway. Photo taken 10/14/01.
A last look at the Spur Interstate 270 and Capital Beltway split at Exit 38. Spur Interstate 270 sees one independent interchange, that with Democracy Boulevard. The freeway merges into Interstate 270 within two miles. From there northward Interstate 270 divides into local and express roadways. Photo taken by Tim Reichard (02/08/03).
Spur Interstate 270 - Northern Terminus
Perspective from Interstate 270 south
Southbound on Interstate 270 at the split with Spur Interstate 270. This is the only signage that displays Spur I-270. Spur I-270 mileposts are in use Southbound however. Photo taken 10/14/01.


  1. "STATE HIGHWAY ADMINISTRATION CELEBRATES OPENING OF I-270/MD 187 (OLD GEORGETOWN ROAD)/ROCKLEDGE DRIVE INTERCHANGE IN MONTGOMERY COUNTY." Maryland Department of Transportation (MDOT) and the State Highway Administration (SHA). November 4, 2003.

Page Updated January 13, 2007.

Additional Info

State Maryland
Mileage 34.40
Cities Bethesda, Rockville, Gaithersburg, Frederick
Junctions I-495, Spur I-270, I-370, I-70
Source: December 31, 2016 Interstate Route Log and Finders List
I-270 Maryland Annual Average Daily Traffic

County From: To: AADT Comp.
Montgomery I-495 Exit 1/ MD 187 127,075
Montgomery Exit 1/ MD 187 Exit 2/ I-270 Spur 117,100
Montgomery Exit 2/ I-270 Spur Exit 4/ Montrose ad 254,975
Montgomery Exit 4/ Montrose Rd Exit 5/ MD 189 234,175
Montgomery Exit 5/ MD 189 Exit 6/ MD 28 258,975
Montgomery Exit 6/ MD 28 Exit 8/ Shady Grove Rd 246,375
Montgomery Exit 8/ Shady Grove Rd Exit 9/ I-370 178,675
Montgomery Exit 9/ I-370 Exit 10/ MD 117 202,975
Montgomery Exit 10/ MD 117 Exit 11/ MD 124 167,475
Montgomery Exit 11/ MD 124 Exit 13/ Middlebrook Rd 139,107
Montgomery Exit 13/ Middlebrook Rd Exit 15/ MD 118 119,175
Montgomery Exit 15/ MD 118 Exit 16/ MD 27 106,075
Montgomery Exit 16/ MD 27 Exit 18/ MD 121 83,675
Montgomery Exit 18/ MD 121 Exit 22/ MD 109 81,875
Exit 22/ MD 109 Exit 26/ MD 80 80,675
Frederick Exit 26/ MD 80 Exit 31/ MD 85 71,675
Frederick Exit 31/ MD 85 Exit 32/ I-70 U.S. 15-40 82,425
I-270 Spur
Montgomery I-495 Exit 1/ Democracy Bl 139,975
Montgomery Exit 1/ Democracy Bl I-270 122,300
Source: 2002 AADTS Report (Maryland Department of Transportation State Highway Administration - Highway Information Services Division)
Frederick inset - 1967 Maryland Official Highway Map.
Interstate 70S defaulted onto U.S. 15 north in Frederick prior to the 1960s completion of the freeway west from Frederick to Hagerstown.