This wonderful museum eloquently run by the US National Park Service has exhibits, photos and news clippings from the 1897 Klondike gold rush, when a Seattle-on-steroids acted as a fueling depot for prospectors bound for the Yukon in Canada. Entry would cost $20 anywhere else; in Seattle it’s free!
The best aspect of the museum is its clever use of storytelling. At the outset you are introduced to five local characters who became stampeders (Klondike prospectors) in the 1890s, and you're then invited to follow their varying fortunes and experiences periodically throughout the rest of the museum. Sound effects and interactive exhibits are used to good effect.
The museum, which opened in 2006, is housed in the old Cadillac Hotel (built in 1889), rescued from a grisly fate after nearly being toppled in the 2001 Nisqually earthquake.