In Comics
Giant-Size X-Men #1 (May, 1975)
Longshot #1 - A Man Without A Past
Base
Xavier Institute, Salem Center, Westchester County, New York State
X-Factor Investigations Headquarters, New York City, New York; formerly Detroit, Michigan; mobile; Xaviers School for Gifted Youngsters, Salem Center, Westchester County, New York; Mojoverse; Cootermans Creek, Australian Outback, Australia; Alcatraz I