From Ancestry.com Wiki
Tewksbury is a town in Massachusetts. It was formed in 1734 and was previously called Billerica. It can be found in Middlesex county and is a part of the Northern registry of deed district. For more information, contact the county at 1009 Main St., Tewksbury 01876. On the attached map, Tewksbury is shown as 8 in Middlesex county.
For information about the state of Massachusetts see Massachusetts Family History Research.