A museum on Seattle's Main Street is named for which Klondike event of the 1890s that made the city a boomtown?

What word names a part of a mug or a briefcase and also a CB radio user's nickname? A muon decays into two neutrinos and one of which particles? A murder suspect named Injun Joe appears in which Mark Twain novel? A museum in Springer, New Mexico, bears the name of which Old West trail that opened in 1821? Which Italian musical direction means to play softly? What musical instrument is "das Klavier" in German? What type of musical decoration often hangs above a baby's crib? Which French composer wrote the 1859 opera "Faust"?