Jeremiah and Catharine moved to Iowa sometime after 1868, when daughter Margarett was born in Pennsylvania.

1880 Census, Black Oak, Mahaska Co., Iowa, p. 280A229
Riggs, Jeremiah, 38, b. PA, parents b. PA, farmer
Catharine, wife, 33, b. PA, parents b. PA, keeping house
William, son, 10, b. PA, at home
Mary, dau, 8, b. PA
Alice, dau., 7, b. PA
Elizabeth, 4, b. PA
Margarett, dau., 2, b. PA