The X-Men were founded by Professor Charles Xavier in 1976, and since then there has always been at least one and sometimes as many as three active X-Men teams at any one time.
| Team | Base of Operations |
Active
|
| X-Men | Xavier's School For Gifted Students, NY |
1976-6/86
|
| X-Force | New York, NY |
1/85-6/86
|
| Australian X-Men | Australia |
6/86-4/87
|
| US East Coast X-Men | Xavier's School For Gifted Students, NY |
6/86-6/91
|
| US West Coast X-Men | San Francisco, CA |
2/87-6/91
|
| European X-Men | France |
3/89-9/90
|
| Texas X-Men | Fort Hooker, Snyder, TX |
6/91-3/92
|
| New York X-Men | Astoria Park, Queens, NY |
6/91-12/92
|
| San Francisco X-Men | San Francisco, CA |
3/92-present
|
| New York X-Men | New York, NY | 2/95-present |
| New Orleans X-Men | New Orleans, LA | 9/95-present |
Several replacement teams have been formed to deal with specific emergencies, usually to cover for absent or missing X-Men teams. Instances include the New X-Men of 1980, who were assembled to rescue the other X-Men from Krakoa, the living island; the team assembled in June 1986 when the majority of the X-Men were taken to the Shi'Ar galaxy; the US East Coast team that was active between March and May 1990, when several of the regular team members were trapped in another dimension by Strife.