COMIC LEGEND: New Mutants came about because Marvel was considering doing a West Coast branch of the X-Men.
STATUS: True
An important point that came up over and over in the early days of Marvel’s expansion of their X-Men line of comics, back when there WASN’T a “line” at all, just a single comic, was that Chris Claremont was not a fan of expanding the line. He knew very well that the more comics there were, the less control he would have over the characters. In the early days, when something like Wolverine’s first mini-series came out, Claremont specifically wrote Wolverine out of Uncanny X-Men for the duration of the mini-series.
Over time, his position slowly became “Well, if it is going to happen no matter what, then I might as well be the one who does it.” For instance, he never wanted Wolverine to have his own ongoing series, but if it was going to happen (and since Wolverine was so popular, it WAS going to happen), then he would write it (and come up with a way to make it distinct enough from the X-Men so that it wouldn’t feel as though it was overlapping with the X-Men adventures, hence the creation of the Patch alternate identity)…
They were still developing their plans, though, when another editor at Marvel forced the issue with the introduction of an idea for ANOTHER X-Men spinoff! The great Peter Sanderson had the story in his classic X-Men tome, X-Men Companion:
“Since the spring of ’81 Weezie (X-Men Editor Louise Jones) and I have on various occasions kicked around the idea of doing a second (X-Men) book,” writer Chris Claremont revealed in The X-Men Companion. “We decided to wait until we found someone (to draw the book) and then think seriously about putting it together.”
“We were afraid that we would go to (Marvel) and say, “Hey, let’s do an X-Men book,” and they would say, “Yes, but the only person available is…” somebody that we wouldn’t be interested in using,” Louise Jones added. “So we were going to keep our mouths shut until the spring. We were going to pick our people and then we were going to say, “Hey, we’ve got a book for you.””
“Right. With three issues in the drawer,” Claremont continued. “And what happened was that while we were pretty much solidifying the concept or at least getting it as much into focus as we felt we needed,
Mark Gruenwald went into (Editor-In-Chief) Jim (Shooter)’s office with a proposal for an alternative X-Men book involving the “loose” members of the original team – Angel, Iceman, Beast, Havok, Polaris – and I suppose any other extraneous mutants that happened to be around, and setting them up on the West Coast as a kind of a…” “X-Men West,” Louise Jones cut in.
“And regardless of the individual merits of the concept, it was way different from what we had in mind,” Claremont continued. “Jim quite properly went to Weezie and said that this proposal had been made to him, and asked if we had any problems with it… or suggestions, or comments. Weezie pointed out, well, we had our own concept in the works, and we’d had it for quite some time. And Jim said, “Oh, okay, well, let’s hear it.” So then we had to put up or shut up.”
“And luckily at about the same time (artist) Bob McLeod had just surfaced (…) and the pieces all meshed together.”
New Mutants debuted at the end of 1982…
https://www.cbr.com/comic-book-legends-revealed-525/