Big Thunder Mountain Railroad is an indoor/outdoor mine train roller coaster located at Disneyland Park at the Disneyland Resort in Anaheim, California. It was designed by Imagineer Tony Baxter and ride design engineer Bill Watkins. Originally designed as part of an expansion to Frontierland in Magic Kingdom in Orlando, Florida called "Western River Expedition," the attraction went through several delays before it was finally constructed, but it was decided to have the attraction built first at Disneyland. It opened on September 2, 1979 in Disneyland's Frontierland.