First Appearance: Uncanny X-Men #215 (March 1987).
Appearances: Uncanny X-Men #215 (referred to).
Years Active: 1941-1945? (see below).
In the same issue that introduced the Crimson Commando, Stonewall, and Super Sabre, the "Yankee Clipper" was referred to. She was a former teammate of the trio of World War Two veterans who was described (by the Crimson Commando, IIRC) in admirable terms. The Yankee Clipper never appeared in the issue itself, however; she was referred to in the past tense, and Roger Stern, author of the Marvel: The Lost Generation series and creator of the Yankee Clipper (II), has stated that the Clipper died during WW2.
No information was given on the Yankee Clipper (I)'s powers, but given her name (a "Yankee Clipper" was a whaling ship) it might be assumed that her powers were sea-related, perhaps along the lines of Namora's.