A haven for summer tourists and winter sport enthusiasts, Wisconsin is famed for its physical beauty and its prodigious production of cheese and dairy products. Richard Nelson Current's compact history reveals the colorful past of America's Dairyland, from early explorers and gangsters to sports heroes and cheeseheads.   Both the Ringling Brothers' "World's Greatest Shows" and Barnum & Bailey's "Greatest Show on Earth" originated in Wisconsin, along with the typewriter, Johnson's Wax, and the first automatic assembly line (for manufacturing automobile frames). Wisconsin inventors contributed to the mechanization of American farms by developing harvesters, reapers, cultivators, threshers, and other machinery. Sen. Robert M. ("Fighting Bob") La Follette brought progressive reform to the state; a few decades later another Wisconsin native, Joseph McCarthy, revealed his agenda as a U.S. senator.   The Gideons, who place Bibles in hotel room nightstands, got their start in Wisconsin, and the state's factories produced most of the 107 steam shovels that dug the Panama Canal. Even before American Motors in Kenosha became Wisconsin's largest employer, Wisconsinites were responsible for such car-related developments as the first four-wheel-drive vehicle and an early tire-patching kit.   To football fans, the capital of Wisconsin is Green Bay, where in 1919 Earl Louis Lambeau organized the Packers. Even during the team's fifteen-year losing streak, Green Bay consisted, as one reporter observed, of "nearly 50,000 wild-eyed maniacs [who] know more about football than any other 50,000 people on the face of the earth."   Fast-paced and entertaining, Current's history chronicles how Wisconsin's homegrown ideas, from the "Wisconsin Idea" of efficient state government to ski-tows and speedometers, made their way into the broader marketplace of American culture.