In 1066, the 6-carucate estate of Thornton was held by Eddiva, but like many Saxon lands, it passed to the Normans and by 1086 was in the hands of Ralph de Mortimer. Thornton remained in the Mortimer family for nearly 350 years until 1425, when the family’s earldom passed to Richard, duke of York.

St. Michael’s Church dates from the 12th century and was one of the chapels, which with their mother church in Pocklington, given to the King between 1100 and 1108. The church is a Grade II list building with several interesting features. The original chapel was extended in the 14th century with the west end rebuilt, including a bellcote, between 1890 and 1892. Built from coursed squared rubble with some cobbles and brick, it has freestone dressings to openings and the bellcote is timber framed. The nave has three bays and the chancel two, both with slate roofs. The nave has buttresses with offsets and two square-headed two light windows with ogee tracery. The chancel has a small round-arched priests' door with a continuous narrow chamfer. The church has an early 19th century organ case with inlaid wood.