"Inside the Beltway" is an American idiom used to characterize matters that are, or seem to be, important primarily to officials of the U.S. federal government, to its contractors and lobbyists, and to the corporate media who cover them—as opposed to the interests and priorities of the general U.S. population.
The Beltway refers to Interstate 495, the Capital Beltway, a circumferential highway (beltway) that has encircled Washington, D.C. (the capital of the United States) since 1964. Some speakers of American English now employ the word as a metonym for federal government insiders (cf. Beltway bandits), and the phrase "inside the Beltway" is used as a title for a number of political columns and news items by publications like the Washington Times. American University's magazine and columnist John McCaslin.
In the White House of Richard M. Nixon, it was said that Watergate would become serious only if it 'got outside the Washington Beltway', if the depths of the disgrace were understood by the American people. In 1974, the truth of Watergate flooded the country, and the Nixon presidency ended.
It can be said that the myriad doubts about the Warren Commission's findings in the death of President Kennedy represent a reverse situation. The doubts would never be taken seriously until they were inside the Beltway, in the halls of Congress, the courts and the White House.— Nicholas M. Horrock, (October 12, 1975) The New York Times: p. 230.
The 2016 Democratic Presidential Candidate Bernie Sanders was quoted in an interview with Chris Matthews as saying he is not "an inside the Beltway guy." In the context of the interview, it appears that Bernie Sanders used the term to distinguish the American people from those who work on Capitol Hill.
The following cities and counties are located entirely or partially inside the Beltway: