Ayn Rand wrote the book “The Fountainhead”. It was published in 1943, as the question says. This was her first successful novel, and had a long road ahead of it to get published and the success it enjoys today. At least twelve publishers completely rejected the novel at first. The first editor that picked it up literally risked his job to get iti edited and get it published.
When it was first released, it had incredibly mixed reviews. It was one of those books that was either incredibly beloved or incredibly hated by everyone that read it. However, through word of mouth and the power that recommendations from friends has, it became one of the most famous novels. It’s still Rand’s most famous work.