Is this the William Maxwell found in the 1790 census of Fayette County, PA city of Tyrone? There is also a John Maxwell on the same page. The names you mention are in the census records of Washington Co., PA - Smith Twp
My interst is in the John Maxwell I found by following the Washington Co. census information. In 1850 John Maxwell is 65 and has a wife named Ann, age 64 - both were born in Ireland. Others mentioned born in PA, living with John & Ann, are Sarah, John, Jane & Allis Jane Whitaker.
I do not have much information on the Maxwell family. My starting point was trying to locate (Mary?) Elizabeth Maxwell who married James Flynn. They lived in Fayette Co, PA until Elizabeth's death in the mid 1880's. They had twin sons, FRANCIS & JOHN.
Elizabeth Emberton Bailey - firstname.lastname@example.org