[4] That same year, he settled in Dutchess County, New York with a British military pension of half pay.

According to a short biography produced by his daughter, Harriet Weissenfels Baker, in an attempt to obtain compensation for her father's monetary losses resulting from his service in the American Revolution she reported that, "Following his principles rather than the advice of friends, he early joined the side of the revolutionaries in the American Revolutionary War."

However, in April 1782, New York raised two regiments of Levies to defend the state's northern frontier (Mohawk Valley) from Canadian irregulars and their Native American allies.

The American forces were under the overall command of Colonel Marius Willet, with whom Weissenfels had served earlier in the war.

In July 1781, Willet and Weissenfels led the militia in the Battle of Sharon Springs where they ambushed a force of Indians and Loyalists under the command of John Doxtader.

In October, they led the militia against a mixed force under the command of Major John Ross at the Battle of Johnstown.

A forced march through a heavy snowstorm brought the militia within two miles of the Loyalist camp by nightfall of October 29, but Willet decided against a night attack in the storm.

In February, 1783, George Washington directed Willet to capture Fort Ontario, but the Americans gave up the attempt when the possibility of surprise was lost.

Washington visited the Mohawk valley in 1783 and he instructed Willett to improve the roads and waterway to Lake Oneida.

However, with regard to his second request they wrote, "With respect to his being put on a footing with foreign officers, who were in the service of the United States, the Committee are of the opinion it cannot be done consistently with the principles of general justice."

However, Weissenfels' grandchildren continued to press their claim with the last living grandchild, Lucy A. Baker, requesting Congressional action in 1877.

Congress rejected her final plea on Jan. 21, 1877, 102 years after her grandfather had given up his British Army pension and any chance of obtaining the promised land to join the Revolution.

By 1787, Weissenfels' financial difficulties were so severe that on February 23, 1787, the New York State Legislature passed a bond, "from Frederick Weissenfels to the people of the state, for such sum as shall be found due him, to be paid in such sums as shall be found due from him to them, to be paid in certificates issued by the treasurer, to discharge him from the suit against him by the people."

The position was likely obtained for him by Abraham Redwood Ellery, a wealthy New Orleans planter, lawyer, and the husband of his granddaughter, Sarah Charlotte Weissenfels.

His son and fellow Revolutionary soldier, Charles, who was the Collector of Customs in New York City in 1795, died that same year.