Madsen family history. From Denmark to the Bay Area of California.

I want to learn more about my Danish side of the family. My great grandmother was Mary Madsen Fortin born in 1902 in Illinois to Anton N Madsen and Anna B Hansen Madsen. Both from Denmark and immigrated about the 1890’s to the USA. My great grandmother had several brothers. Nelson Madsen, Harry Madsen, Albert Madsen, Howard Madsen, and Arthur Madsen. All whom ended up in the Bay Area of California. I have reached a dead end when searching to see if any of them had children.