Edmund Hillary: Before 1953, Mount Everest loomed much larger than 29,035 feet in the eyes of mountaineers. All expeditions had failed, leaving 13 dead. But when a beekeeper and his Sherpa scaled it, reaching an altitude normally reserved for aircraft, the world's last unreachable spot was finally tamed.
Marco Polo: The Venetian merchant traveled more than three years just to reach the Mongol Court, crossing deserts and mountains (all the while dodging potentially murderous bandits). By the time he finally returned home in 1295, Polo had spent almost 25 years covering some 33,000 miles.
Lewis and Clark: Lewis got the job primarily because he was Thomas Jefferson's secretary; Clark could barely write and retired from the army due to poor health (including severe constipation). But over 28 months they traveled to the Pacific Ocean and back, opening up the West.
Moses: An adventurer from the start (as a baby he rafted the Nile in a basket to escape death), Moses convinced the Pharaoh to let his people go, only to be pursued by armies until that Red Sea incident. Not the swiftest traveler, but you can't fault the results after 40 years in the desert.