From Ancestry.com Wiki
Groton is a town in Massachusetts. It was formed in 1655. It can be found in Middlesex county and is a part of the Southern registry of deed district. For more information, contact the county at 173 Main St., Groton 01450. On the attached map, Groton is shown as 10 in Middlesex county.
For information about the state of Massachusetts see Massachusetts Family History Research.