John Jacob Astor's dream of empire took shape as the American Fur Company. At Astor's retirement in 1834, this corporate monopoly reached westward from a depot on Mackinac Island to subposts beyond the confluence of the Missouri and Yellowstone Rivers.   Fur Traders, Trappers, and Mountain Men of the Upper Missouri focuses on eighteen men who represented the American Fur Company and its successors in the Upper Missouri trade. Their biographies have been compiled from the classic ten-volume Mountain Men and the Fur Trade of the Far West, edited by LeRoy R. Hafen.   These chapters bring back movers and shapers of a great venture: Ramsay Crooks, the mountain man who headed the American Fur Company after Ast∨ Kenneth McKenzie, "King of the Missouri;" Gabriel Franchere, survivor of the Astorian disaster; Charles Larpenteur, commander of Fort Union and fur-trade chronicler. Here, too, are the fiery William Laidlaw, ambitious James Kipp and John Cabanne Sr., diplomatic David Dawson Mitchell and Malcolm Clark, goutish James A. Hamilton (Palmer), controversial John F. A. Sanford and Francis A. Chardon, easy-going William Gordon, and ill-fated William E. Vanderburgh. Completing this memorable cast are Alexander Culbertson, skilled hunter; Auguste Pike Vasquez, mountain man; Henry A. Boller, educated clerk; and Jean Baptiste Moncravie, trader and raconteur.