1920 Census, Rock Valley, West 3rd St., Sioux Co, IA
202/207 Silas Rudd, Silus, Head, owns home, age 68, b. IL, parents b. PA, House Painter
Elizabeth, wife, age 47, immigrated 1847, naturalized, year unknown, she and parents b. Germany
Helmer, Edward, son-in-law, age 26, b. IL, parents b. Germany, laborer garage
Helmer, Irene, daughter, age 21, b. IA, father b. IL, mother b. Germany

According to probate, he was given a guardian. In 1870 there is a Silas Rudd, age 13, in Owen Twp., Winnebago Co., IL -- he is in the poorhouse and called a pauper. Even with the age difference, I think he is the one b. 185070