Eventually, he acquired a patent for La Val from the Calvert family who were the first proprietors of colonial Maryland.

[2] He became quite prosperous and his Middle Plantation in Davidsonville, Maryland and La Val were "as luxurious and courtly as any of the manors of the English gentry.

Duvall had purchased sizeable tracts of land, including Catton which was later known as Belair,[6] as well as the Middle Plantation in Davidsonville, Maryland.

In 1705, his son, John Duvall and his wife Mary deeded land to Queen Anne Parish to construct St. Barnabas Church.

[7] His notable descendants include Harry S. Truman, Barack Obama, Dick Cheney,[7][8] Wallis Simpson, and Robert Duvall.