John Kopp, son of Joseph and Barbara Kopp, brother of William Kopp:

1900 Baldwin, Randolph County, IL census:

Kopp, John, head, 8/1850, IL
Kopp, Lizzie, wife, 4/1848, Germany
Kopp, Lizzie, daughter, 1/1887, IL
Kopp, Joseph, son, 1/1882, IL
(John Kopp married Elizabeth Kopp (Mrs.) on 11/17/1877 in Randolph County, IL. I don't know if she was married to another Kopp or they just didn't have her maiden name.)

1910 Baldwin, Randolph County, IL census:

Kopp, John, head, 59, IL
Kopp, Lizzie, wife, 60, Germany
Kopp, Joseph, son, 28, IL
Kopp, Lizzie, daughter, 23, IL

1920 Ellis Grove, Randolph County, IL census:

Kopp, Joseph, head, 37, IL
Kopp, Esther, wife, 34, IL
Kopp, Mildred, daughter, 7, IL
Kopp, John, son, 5, IL

1930 Ellis Grove, Randolph County, IL census:

Kopp, Joseph, head, 48, IL
Kopp, Esther, wife, 44, IL
Kopp, Mildred, daughter, 17, IL
Kopp, John, son, 15, IL

Kim Mohler