NAMED AFTER TREES that quiver in the slightest breeze, Aspen, Colo., ironically, has proven unshakable. When other silver-mining boomtowns of the 1800s went bust, Aspen endured—partly because the county courthouse was there, partly because it was a cattle- and sheep-ranching stronghold. In 1947, it cannily evolved into a winter vacationland when Aspen Mountain opened the world’s fastest ski lift (it still took 45 minutes to ferry one-person-per-chair to the top). Now stuffed with urbane offerings you rarely find at elevations of 8,000 feet and thanks to new direct flights from cities like Chicago and L.A., Aspen lures...