First Appearance: Marvel Mystery Comics #49 (November 1943).
Golden Age Appearances: Marvel Mystery Comics #49-85, Miss America #1-2, All-Winners #19 & 21, All-Select #11, Blonde Phantom #12-14, Sun Girl #1.
Modern Appearances: Giant-Size Avengers #1, Marvel Premiere #29-30, Invaders #6 & #35-41, Invaders v2 #1-4, Avengers #185-186, Web of Spider-Man #4, Thor Corps #2, 4 #1, She-Hulk v2 #22, Citizen V & the V-Battalion v1 #2, v2 #1.
Years Active: 1942-?

Madeline Joyce is the ward of James Bennett, a wealthy financier who is sponsoring a project to study electrical energy. This study is being done in a converted lighthouse along the coast (this is outside of New York City, so it might be along Long Island or Connecticut, but since there's a lighthouse involved I'm gonna assume that it's Connecticut). One night a curious Madeline lets herself into the lighthouse to look around. Sure enough, this is the same night that a massive thunderstorm blows up, and the lighthouse is struck by lightning while Madeline is inside. She receives a massive dose of electricity and is knocked out.

When she wakes up she finds that she has superpowers. Naturally she decides to use them to fight crime, evil, and the Axis powers. After a number of solo adventures, including a serial that lasted from Marvel Mystery #75-86, she joined the All-Winners Squad along with  Bucky (II), Captain America (II), Human Torch (I), Namor the Sub-Mariner, Toro, and the Whizzer. When the Squad ended, she continued on in various comics, appearing as late as 1948, but like the rest of the Timely heroes she disappeared before the Fifties came around.

Then, almost thirty years later, she was brought back and her history somewhat revised. It was revealed that she had begun as a solo hero before joining the Liberty Legion. Then, along with the Whizzer, she'd left the Liberty Legion for the Invaders, and after the war joined some of the Invaders in the All-Winners Squad. She and the Whizzer were romantically linked since their time together in the Liberty Legion, and when the Squad disbanded in 1949 the Whizzer and Miss America got married and went to work for the government doing security work.

In 1960 the Whizzer and Miss America were working security in a nuclear plant when it was sabotaged by their old opponent Isbisa, thus causing the pair of heroes to be irradiated. Madeline was pregnant at the time, and the radiation affected her fetus, causing it to be born a radioactive mutant. (This child, Bob Jr., eventually grew up to become Nuklo.) Following this Madeline and Bob toured Europe, and during this trip Madeline became pregnant again. The child was stillborn, and Madeline died during childbirth, on Wundagore Mountain, where she was buried.

Later still it was revealed that the the Whizzer, with Miss America, was a founding member of the V-Battalion's Penance Council. In 1953 she attended the funeral of Union Jack (II).

Originally, in the Golden Age, Miss America was a powerhouse; she could fly, has X-ray vision, had the "strength of a thousand men," and the "wisdom of the ages." When she was revived as a member of the Liberty Legion and her story retold, she was given only flight.

Useful Miss America Site

Miss America. Another of Eric Colley's efforts.