It was named after William Wentworth, 2nd Earl of Strafford in the mistaken belief that he was the ancestor of governor John Wentworth – although they were distantly related, William had no descendants.

Strafford County constitutes a portion of the Boston-Cambridge-Newton, MA-NH Metropolitan Statistical Area as well as of the greater Boston-Worcester-Providence, MA-RI-NH-CT Combined Statistical Area.

It is estimated to be New Hampshire's county with the highest percentage growth over the 2010–2019 period.

As of the census[10] of 2000, there were 112,233 people, 42,581 households, and 27,762 families living in the county.

The racial makeup of the county was 96.29% White, 0.63% Black or African American, 0.21% Native American, 1.39% Asian, 0.05% Pacific Islander, 0.30% from other races, and 1.14% from two or more races.

24.80% of all households were made up of individuals, and 8.20% had someone living alone who was 65 years of age or older.

The largest cities in Strafford County are Dover (population) and Rochester (land area) .

As of the 2010 United States census, there were 123,143 people, 47,100 households, and 29,862 families living in the county.

There were 51,697 housing units at an average density of 140.1 per square mile (54.1/km2).

[12] The racial makeup of the county was 93.8% white, 2.6% Asian, 1.0% black or African American, 0.2% American Indian, 0.5% from other races, and 1.9% from two or more races.