The Museum was intended to open on November 13, 1951, the centennial of the Denny Party landing at Alki point, but construction delays bumped the official event by a few months. Instead, the date of February 15 was chosen to honor the centennial of Arthur Denny, Carson Boren, and William Bell's selection of land claims in what is now downtown Seattle.
MOHAI's opening ceremonies began at 8:00 p.m., but the celebration was signaled a half hour earlier with the blowing of an old whistle used in the Alaska-Yukon-Pacific Exhibition held on the University of Washington campus in 1909. The whistle was from a Russian gunboat acquired by the United States in the purchase of Alaska.
Master of Ceremonies was Stephen F. Chadwick, a Seattle attorney. Speakers included E. L. Blaine, Emil Sick, Governor Arthur Langlie, and Mayor William Devin (1898-1982). Mrs. Theodore Plestcheeff, president of the Seattle Historical Society, made the formal presentation of the building to the city.
A ribbon was cut by Victoria Watt, great-great-granddaughter of Seattle founder Arthur A. Denny, signaling the opening of the museum to patrons. MOHAI's original hours for public viewing were Tuesdays through Fridays, 11:00 a.m. to 5:00 p.m., Saturday from 10:00 a.m. to 5:00 p.m., and Sundays and holidays from noon to 5:00 p.m.