Pratt rose to became a member of the corporation's executive committee and, from the 1920's until 1968, served on GM's Board of Directors. He was later a company Vice President and is credited with supporting the idea of purchasing what became the Frigidaire Division of GM and given credit for overseeing the development of the coolant, Freon.
In 1932, he bought "Chatham Manor", an expansive Georgian, Colonial mansion on the Rappahannock River in Stafford County, opposite Fredericksburg as his future retirement home. He paid $150,000 in cash for the property, roughly the equivalent of $2.6 Million in 2007. By moving to "Chatham", he was -- in effect --moving back to his hometown.
Mr. and Mrs. Pratt were extensively involved in the local community in their later years and were quiet philanthropists supporting University programs in Virginia and college educations for worthwhile community young people who had been identified for their potential by other religious and community leaders. In no endeavor did they seek publicity or recognition.
After his wife died, Pratt continued to socialize with his former childhood friends in Fredericksburg, walking regularly into the city even though he could have afforded a chauffeur and any car in the GM fleet. His rumpled appearance belied his comfortable station in life while he continued his life-long associations and played in weekly penny-ante poker games with his friends.
Lillian Pratt died in 1947 and willed her extensive jewelry collection to the then-new Virginia Museum of Fine Arts in Richmond, Virginia. Since the 1920s, encouraged by a family acquaintance, the businessman Armand Hammer, she had accumulated a large collection of Peter Carl Fabergé jewelry, including five Fabergé eggs; the Revolving Miniatures, Pelican, Peter the Great, Czarevich, Red Cross with Imperial Portraits examples, as well as pins and bracelets which were being sold by the then-new government of the Soviet Union to raise capital for the Soviet state. This collection, at the time the largest private collection of such items, had been initially acquired through purchases on her Lord & Taylor Department Store charge account. The "Lillian Pratt Collection" at the Virginia Museum of Fine Arts is a key part of that institution's exhibits. Lillian Pratt is buried in Tacoma, Washington.
The remainder of his estate was auctioned with the proceeds donated to the University of Virginia (his alma mater), Virginia Tech, and Johns Hopkins University.
His cremated remains rest in Oak Hill Cemetery in Fredericksburg, Virginia.