He served in
the West Church from June 7, 1780, to his death on October 19, 1812. He donated money and land to the church. He was a
Democratic-Republican and often preached this political philosophy to his congregation. During his pastorate, the meetinghouse was pulled down and a new one was erected. Thatcher was frequently asked to give guest sermons in other churches, including one on
Christmas Day in
Dedham's Anglican church, of which 20 were published. In 1800, Colburn Gay of Dedham wished to marry Sarah Ellis of
Walpole. The laws at the time said that a wedding must take place in the town of the bride, however Gay insisted that Thatcher preside. Thatcher was the minister in Dedham's third parish, however, and could not officiate outside of the town's borders. To resolve this dilemma the couple stood on the Walpole side of Bubbling Brook, and Thatcher stood on the Dedham side. They were married across the stream and had two children before Sarah died in 1810. After
Jason Fairbanks was hung for murdering his girlfriend in front of a crowd of 10,000, Thatcher published a sermon in which he wondered if Fairbanks' hanging and the "riot and confusion" at the end of the day were caused by a hellish legion "of obstreperous, incarnate fiends, who paraded the streets of this peaceful village." ==Legacy==