Thaddeus Defrees was born in Boston, MA on September 27, 1855.  His parents were Georgianna and William, a machinist.

Defrees's style of painting shows strong influence of the French Barbizon School.   He was active in the White Mountains from at least 1877 until his death.  He exhibited at the Boston Art Club in January, 1878.  He was artist-in-residence at the Thorn Mountain House and, later, the Wilson Cottages.

The Proctor family of Jackson, NH was related to the Wilsons of Wilson Cottages.  Alice Protor has related that the Proctors always referred to Defrees as "Jan."

Defrees died suddenly while traveling in Italy.  A Memorial Stone for Defrees can be found in the Southborough Rural Cemetary in Southborough, MA.