I didn't find an Ann Howard in New London County.
1870 Waterford, New London, CT
James Johnson, b. CT, 40, farmer
Louisa, b. CT, 39
Alonzo, b. CT, 18, farmer
Louisa, b. CT, 16
I didn't find either one of his marriages online.
Alonzo Johnson, b. CT, 29, farmer
Anna M., [assume she was Anna Greenfield], b. CT, 19
Alonzo, b. CT, 1
The Waterford Town Clerk, www.waterfordct.org/town-clerk
has the early marriage records.
The Waterford Historical Society, www.waterfordhistoricalsociety.org/
might have more information. Successful Searching!