In 1870s/80s America, were wills common practice? What would happen to someone's money upon their death?

I am writing a novel about a man in the 1870s/80s who has a substantial amount of money that he inherited from his father. My character, Baker, is unmarried with no children, and until presently his will has left the bulk of his money to his only surviving brother, Jasper. He wants his common law wife and her children to inherit the money upon his death. Does he need a will to change this or would it just be expected that his common law wife would inherit his fortune?