Formal planning of the Capital Beltway began in 1950 and it was included as part of the Federal Aid Highway Act in 1956 even before construction actually commenced in 1957. Although initially known as the 'Washington Circumferential Highway' in planning stages, a number of names were proposed for the highway including 'Colonial Beltway,' 'Colonial Parkway,' 'Capitol Beltway,' and 'Capital Ring' before the designation 'Capital Beltway' was retained in June 1960. The Maryland side of the Beltway was primarily designed by the engineering firm, Michael Baker Corporation.
Built in the winter of 1963, the Capital Beltway Bridge over Cabin John Creek was one of the final sections of road to be constructed prior to the opening of the Maryland side (I-495) in August 1964. The northbound and southbound sides of the bridge are actually separate structures, each of a length of 253 feet, running parallel to each other with only a few inches of space between. The bridge initially comprised a six lane beltway (three per side) but was widened, in 1970, to accommodate eight lanes of traffic (four per side) in an ongoing effort to expand the capacity of the beltway. The total width of the eight lane bridge is approximately 72 feet. The bridge has an average daily traffic of 38,000.