The federal establishment here comes in all shapes and sizes.

While many people outside Washington think of THE GOVERNMENT as the Pentagon, State Department or Congress, there is life (and people) outside those glamor spots. In fact, most federal workers here don't work at any of those places and probably find them as strange as do the residents of Decatur, Ill., or Deer Lodge, Mont.

The number of federal civil servants here -- excluding employes of the Central Intelligence Agency and the National Security Agency, who decline to be counted -- is 344,657. Those employes, 11 percent of the U.S. government work force, do a lot besides making up treaties with the Soviets, helping farmers grow better tobacco or getting involved in -- as participants or investigators -- things like the Iran-contra affair.

Members of Congress who preach against the ever- expanding bureaucracy may not spend enough time at their offices, which are expanding like anything else in the government.

The White House takes obvious delight in citing the shrinkage of the federal work force under President Reagan. In fact, the number of federal workers nationwide is 3,065,822, and despite creative head-counting techniques and careful omissions (like not counting the growth in the U.S. Postal Service or the Defense Department), the government has 20,000 to 40,000 more employes than it did before Reagan took office.

If growth is bad, neither side has much room to criticize the other.

If the legislative branch, controlled directly by Congress, were considered a single federal agency, it would be the largest government operation in the Washington area.

Government data, as of March, show that there were 34,766 legislative branch employes here (18,700 of them working for members of Congress or on committee staffs), making Congress second only to the Navy as the area's biggest civilian federal employer. The Navy has 36,953 civil servants based here, and that number has actually been going down slightly as the size of the congressional work force has been going up.

The Department of Health and Human Services is the third biggest federal employer here with 28,712 workers, followed by the Army's 28,000 civilians, the Postal Service, with 20,639 employes, the departments of Justice (18,137), Labor (17,964) and Agriculture (11,897), the General Services Administration (8,209), and the Veterans Administration (6,250).

The distinction of being the smallest federal presence in Washington is shared by Jeanette Gordon, staff assistant of the Susquehanna River Basin Authority, and Barbara Crawford, staff assistant of the Delaware River Basin Commission. They share offices at 1100 L St. NW.

Gordon says she and Crawford don't get bored because they have plenty to do. Their commissioner-bosses, Warner Depuy and George Kanuck, are based in Pennsylvania and Delaware, respectively. When they come to town, the size of their agency work force doubles. Compared with those agencies, the Panama Canal Corp., with six employes here, seems like a bloated bureaucracy. So does the Chicago-based Railroad Retirement Board, one of the few U.S. agencies not headquartered here, which is growing like wildfire, having added an eighth staff member this year.

Maybe Congress should assign investigators to find out what is causing the growth spurt at the Railroad Retirement Board before the situation gets out of hand.