I have a Marilla Spencer (rumor has it they called her Rill) who married a Marcus Langdon. Marilla was born ca 1848 she and Marcus married ca 1864. Cannot locate them in the 1860 census yet.... They moved with the rest of the family to IA. The last census I can locate them is the 1870 Monroe County, IA. They had the following children:
James H., Washington Lee, Wellington F. (who later changed his name to William Frederick), and Charles.
If you think they might be part of your Spencer's I'd love to hear from you.