Neil Gaiman's novel "American Gods" was a project that evolved over several years. While it's challenging to pinpoint an exact timeframe for its creation, it's known that the development of the book spanned a significant period. Gaiman first began thinking about the concepts and ideas that would later become "American Gods" in the late 1990s.
The novel was officially published in 2001, which suggests that Gaiman likely spent several years working on it, including the process of conceptualizing, writing, revising, and editing. During this time, he conducted extensive research into American mythology, traveled across the United States, and drew from a variety of sources to shape the narrative.
The extended development period allowed Gaiman to craft a complex and richly layered story that explores themes of mythology, belief, and the changing cultural landscape of America. It's not uncommon for authors to spend several years working on a novel of this scope and complexity, and the end result was a critically acclaimed and award-winning work that has become one of Neil Gaiman's most iconic novels.