William was born in Ireland on Christmas Day, a Monday in 1786.

William married Martha Smith within the York Presbyterian Congregation on a Tuesday.

William and Martha's first child, James, was born in 1809 in Pennsylvania. The proud parents had their son christened within the same congregation of their marriage less than a year earlier, on February 25, 1810.

At an age of about 24, William was enumerated in the 1810 Federal Census in York County, PA with his newborn son and wife.

William Flanagan purchased property from Thomas Cadawaler in York Borough, which is located on the North side of High Street. This lot is marked as lot number 399 on the general plan of York Borough. William appears to have paid $33.74 for purchase.

William and Martha moved to Jefferson County, Virginia sometime before their son's marriage in 1835. William, Martha, and their daughter, Ann, were enumerated in the 1840 Federal census here.

William was enumerated in the 1850 Federal Census in the 28th District of Jefferson County, Virginia. He lists his occupation as farmer with a real estate value of $11,200. William was living with his wife, Martha, and daughter, Ann Rebecca. His son, James, lived in the neighboring household. The census taker noted that William was blind.

William pays to run an advertisement four times in the Shepherdstown Register. He wishes to rent the farm where he resides near Bakerton to a tenant. This advertisement suggests his failing health.

William died in September of 1855 at his home, Potomac View, at Oak Grove. This location, in a few short years, would become Bakerton. The cause of death was listed as bilious dysentery.