The Klondike Gold Rush Visitor Center and Museum is open Wednesday through Sunday, 10:00 AM to 5:00 PM.
Seattle's National Park Store (aka, the park bookstore) is open Wednesday through Sunday 10:00 AM to 5:00 PM and the online store is open 24/7.
The Outdoor Recreation Information Center in Seattle's Flagship REI store is staffed Thursday through Monday, 10:00 AM to 6:00 PM. Closed Tuesdays and Wednesdays.