Peter was born in 1798 in the Town of Westerlo, a son of John Flagler and Gertje Bogart.
Peter grew to maturity in Westerlo and was a farmer by occupation. He was also elected to the legislature of the town. 
Marriage & Children
Peter married Letta Lawrence born at about 1807, a daughter of William Lawrence at about 1825 in Westerlo. Their children:
- Chester Flagler, born at about 1826
- Morgan Flagler, born at about 1828
- John Flagler, born at about 1829
- William Flagler, born at about 1831
- Juliaette Flagler, born at about 1834
- Peter H. Flagler born in 1840
- Almira Flagler, born at about 1847
Peter died in 1866, and Letta died in 1893 at age 89 years. Both are buried at the Onesquethaw Cemetery in Clarksville.
- Landmarks of Albany county, New York, Edited by Amasa J. Parker