Interstate 370

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Interstate 370

I-370 highlighted in red
Route information
Auxiliary route of I-70
Maintained by MDSHA
Length2.54 mi[1] (4.09 km)
NHSEntire route
Major junctions
West endSam Eig Highway in Gaithersburg
Major intersections
East end
MD 200 Toll in Derwood
CountryUnited States
Highway system
MD 368 MD 370

Interstate 370 (I-370) is a 2.54-mile (4.09 km) Interstate Highway spur route off I-270 in Gaithersburg, Maryland, to the western end of the Maryland Route 200 (MD 200, Intercounty Connector) toll road at an interchange that provides access to the park and ride lot at the Shady Grove station on the Red Line of the Washington Metro. Despite the number, I-370 does not connect to I-70 itself. The road continues to the west of I-270 as Sam Eig Highway, a surface road. Along the way, I-370 has interchanges with MD 355 and Shady Grove Road. The freeway was completed in the late 1980s to connect I-270 to the Shady Grove station. I-370 was always part of the planned Intercounty Connector but was the only segment to be built at the time. The opening of MD 200 east of I-370 resulted in the truncation of I-370 to the interchange with MD 200 and the redesignation of the road leading into the Shady Grove station as MD 200A.

Route description

I-370 at MD 355, from top-left to center-right

I-370 begins a short distance to the west of the I-270 interchange in Gaithersburg, Montgomery County, heading northeast as a six-lane freeway. Southwest of this interchange, the road continues as Sam Eig Highway (named after Washington real estate developer Sam Eig)[2] which interchanges with Washingtonian Boulevard before becoming a surface road. The highway passes woods to the northwest and a shopping center to the southeast as it reaches an interchange with I-270. From this point, I-370 turns east and runs between residential neighborhoods to the north and business parks to the south, with trees separating the road from these areas. The freeway curves northeast again and comes to the MD 355 interchange. Past this, the highway passes more commercial development before reaching a bridge over CSX's Metropolitan Subdivision railroad line. A short distance later, I-370 comes to a trumpet interchange with MD 200A, a road that provides access to Shady Grove Road and the Shady Grove station of Washington Metro's Red Line. At this point, I-370 ends and the freeway continues east as MD 200 (Intercounty Connector), a toll road.[1][3]


View east at the west end of I-370 at Sam Eig Highway in Gaithersburg

What is now I-370 was originally proposed as part of the Intercounty Connector in the late 1970s. The I-370 freeway opened on December 17, 1988, connecting I-270 to the Shady Grove station.[4] After three and a half years of construction, the freeway was four lanes wide and 2.5 miles (4.0 km) long.[4] Its construction cost $169 million (equivalent to $363 million in 2022[5]), with federal funds paying for 90 percent of the cost.[4] The state of Maryland's portion of the cost was funded with a portion of the proceeds of a $0.05-per-US-gallon ($0.06/imp gal; $0.01/L) gas tax increase in 1987.[6] Prior to its opening, driving from I-270 to the Shady Grove station involved exiting at Shady Grove Road and passing six traffic lights to arrive at the station.[4] Upon its opening, the remainder of the Intercounty Connector was planned but not yet built.[7] At the time, it was the fourth shortest Interstate, after I-878 in New York, I-375 in Detroit, and I-395 in Baltimore.[4]

In 2007, construction began on MD 200, which was to head east from I-370. At this time, the ramp from Shady Grove Road to westbound I-370 was shifted to a new alignment.[8] In 2009, the lanes along I-370 were shifted to allow for construction of the MD 200 interchange.[9] Construction on this segment of MD 200 was completed in February 2011, with the road opening to traffic on February 23.[10][11] As a result of the completion of MD 200, the eastern terminus of I-370 was truncated to the west end of MD 200, with the freeway connection to the Shady Grove station becoming MD 200A.[12]

Exit list

The entire route is in Montgomery County.

Gaithersburg0.000.00Sam Eig Highway to Fields RoadWestern terminus; road continues west without designation to MD 119
0.430.691 I-270 – Frederick, WashingtonSigned as exits 1A (south) and 1B (north); no exit number eastbound; exit 9A on I-270

Shady Grove Road to MD 355 south – Rockville
Eastbound exit only
1.933.112 MD 355 (Frederick Road) – Gaithersburg, Rockville, Town CenterNo eastbound access to MD 355 south; former US 240
3WMATA Metro Logo small.svg Shady Grove Road – Metro StationSigned as exit 3A (Shady Grove Road) and 3B (Metro Station) eastbound; unsigned MD 200A; commercial vehicles cannot use exit 3B; last eastbound exit before toll

MD 200 Toll east to I-95
Eastern terminus; road continues east as MD 200 Toll (Intercounty Connector)
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. ^ a b c Highway Information Services Division (December 31, 2015). Highway Location Reference. Maryland State Highway Administration. Retrieved August 10, 2016.
  2. ^ Jewish Washington: "Real Estate Boom" retrieved September 18. 2014
  3. ^ Google (July 2, 2011). "overview of Interstate 370" (Map). Google Maps. Google. Retrieved July 2, 2011.
  4. ^ a b c d e Hankin, Sam (December 22, 1988). "2.5-Mile Interstate Opens to Shady Grove: Congestion on Side Roads Expected to Ease". The Washington Post. p. Md21. ProQuest 139264766.
  5. ^ Johnston, Louis; Williamson, Samuel H. (2023). "What Was the U.S. GDP Then?". MeasuringWorth. Retrieved December 19, 2023. United States Gross Domestic Product deflator figures follow the Measuring Worth series.
  6. ^ Barnes, Robert (April 29, 1987). "Md. Gas Tax Fuels Washington Area;Pr. George's, Montgomery Gain $284 Million for Transportation". The Washington Post. p. B1. ProQuest 306862272.
  7. ^ Vick, Karl (February 3, 1997). "Md. Tollway Remains a Road Not Taken". The Washington Post. p. A01. Retrieved January 26, 2011.
  8. ^ "Intercounty Connector". The Washington Post. 2011. Archived from the original on October 3, 2012. Retrieved June 14, 2015.
  9. ^ "SHA to Temporarily Shift Lanes Along I-370 for Intercounty Connector Construction". Maryland State Highway Administration. June 18, 2009. Retrieved January 26, 2011.
  10. ^ Dresser, Michael (February 7, 2011). "First phase of ICC to open Feb. 22". Baltimore Sun. Retrieved February 7, 2011.
  11. ^ Liu, Mimi (February 23, 2011). "More than 10,000 vehicles travel on first stretch of the ICC Wednesday morning". The Gazette. Retrieved February 23, 2011.
  12. ^ Highway Information Services Division (December 31, 2010). Highway Location Reference. Maryland State Highway Administration. Retrieved August 10, 2016.

External links