The word ""marshals"" evokes tall-in-the-saddle loners shooting it out with outlaws at Tombstone, and laconic stoics braving mobs of angry segregationists. Yet, as this engrossing history details, these ""general practitioners within the law enforcement community"" have represented federal authority at the local level throughout America's stormy 200-year-history. Calhoun, who in 1984 became the first Historian for the US Marshals Service, builds a deft narrative on an impressive base of primary materials he came across while at that post. He shows how the marshals and their deputies, lacking clearly defined duties (and even a central administration until 1956), have displayed remarkable versatility: taking every national census through 1870; confronting Whiskey Rebels; stopping Filibusters in Central America; chasing fugitive slaves; administering federal decrees in the conquered South and the frontier West; and guarding the Mexican border during the Madero revolution of 1910. As ""adept in accounting procedures and pursuing outlaws, in quelling riots and arranging court sessions,"" they saw the FBI and other specialized agencies usurp their duties for much of the 20th century. This organizational impotence ended when the Kennedy Administration called on the marshals to protect James Meredith during his 1962 enrollment at the Univ. of Mississippi; and their roles continued to expand in later administrations as they faced antiwar protesters marching on the Pentagon in 1967, American Indians occupying Wounded Knee, and drug kingpins. A solid, unaffected history of Americans who ""took upon themselves the difficult and dangerous task"" of enforcing the law of the land, and of the almost maddeningly improvisational way they have been used.