The 1917 Henderson Model G was terrifically modern for its time: It came with a three-speed gearbox, kickstarted, clutch, and rear drum brake. Another bike once owned by Steve McQueen, this Model G is one of just four known examples with the optional generator that powered the front and rear lamps and the horn. Estimated price: $135,000 to $175,000. Courtesy Mecum Auctions

This 1907 “Strap Tank” (for the steel bands holding the fuel and oil tanks to the frame) was the 94th bike Harley-Davidson even built. Mecum calls it “the best unrestored “strap tank” Harley in the world.” Estimated price: $800,000 to $1,000,000. Courtesy Mecum Auctions

It wouldn’t be a real motorcycle collection if it didn’t somehow involve Steve McQueen. Bullitt owned this 1915 Cyclone, equipped with a V-twin that produced 45 horsepower, and no brakes. Estimated price: $650,000 to $750,000. Courtesy Mecum Auctions

In 1913, the Minneapolis Motorcycle Company informed customers, “as to gracefulness of outline and sturdiness of build,” its bikes were “all the most exacting buying could demand.” This Model S-2 De Luxe Twin has a two-speed gearbox and comes with original paint.

In 1912, the Minneapolis-based Theim Manufacture Co. sold this Model G two-speed, which produced some four horsepower from a 400cc engine, for $200. Mecum says it’s “remarkably complete,” including a backrest and Klaxon horn, but a new front wheel would be a good idea for anyone who wants to ride. Estimated price: $65,000 to $75,000. Courtesy Mecum Auctions

Before the “Merkel” name was associated with Europe’s most powerful woman, it was a Milwaukee-based motorcycle maker with visible influence on its neighbor, Harley-Davidson. This 1911 Flying Merkel was made for racing and is in remarkable condition. Estimated price: $350,000 to $400,000. Courtesy Mecum Auctions

This 1907 “Strap Tank” (for the steel bands holding the fuel and oil tanks to the frame) was the 94th bike Harley-Davidson even built. Mecum calls it “the best unrestored “strap tank” Harley in the world.” Estimated price: $800,000 to $1,000,000. Courtesy Mecum Auctions

This Indian was the first motorcycle off the line in 1942, the last year the motorcycle company produced four-cylinder bikes. It’s been restored, and is sold with the title. Estimated price: $85,000 to $110,000. Courtesy Mecum Auctions

One of the newest bikes counted among Cole’s “main attractions,” this 1942 “big tank” Crocker was restored in the early 1980s. It’s one of the last bikes Al Crocker ever built; the war interrupted his production and he didn’t restart in peacetime. Estimated price: $300,000 to $350,000. Courtesy Mecum Auctions

By the late 1920s, the increasing popularity of dirt racing and hill climbs called for longer frames, chains on the rear wheels, and more horsepower. This 1929 Excelsior OHV Super X obliged. Estimated price: $105,000 to $120,000. Courtesy Mecum Auctions