Harriet or better known as Hattie L. Foster was born on either on 23 or 24 December 1857 in Oak Orchard, Orleans County, New York to John W. Foster and Mary E. Parker. These birth dates come from Mary's application for Civil War widow's pension. Mary E. Foster's application for widow's pension dated 10 July 1863 listed dependents are:
- Marcena F. who will turn 16 11 March 1867
- Ermina F who will turn 16 18 May 1868
- Hattie L. who will turn 16 23 Dec. 1873
However, Mary's sister Sarah A. Maynard affidavit states: Sarah A Maynard of Knowlesville, Orleans, New York stated she attended Mary E Foster at Oak Orchard on 24th December 1857 at which time and place she was delivered of a female child, what was afterwards named Hattie L. Foster. -- deposition taken 20 November 1866.
It doesn't really make any difference whether Hatti was born on 23 Dec 1857 or 24 Dec 1857. Since these are the only 2 documents I've found so far, I'm going with 23 Dec 1857 as it is the date given by Hattie's mother.