From the earliest record of the Society of Friends on Long Island:
The children of James and Sarah Cock, borne Killingworth
Mary Cock ye daughter of James & Sarah Cock, was borne ye 1st day of ye 11th Mo. 1655. [1 Jan 1655/56]
[Even if true of most of the children, the birth of Mary may not have occurred in Killingworth on Matinecock in Oyster Bay, Long Island, as her father did not purchase land there until 1662. The family appears to have been living in Southold at the time of Mary's birth.]