Robert Blackwell was the progenitor of the Blackwell family in New York and New Jersey. He was an Englishman of good lineage. The year that Robert Blackwell sailed to America, and the identity of the ship that carried him forth, are unknown. He may have entered America at Sandwich, Massachusetts or at some other New England port. During the mid to late 1660's Robert Blackwell was a freeholder at Newtown, Long Island, and built an historic house at Ravenswood, Long Island.

But shortly after his arrival in Long Island, Robert Blackwell settled amongst the founding settlers at Elizabeth-town, where he bacame a merchant. There is an early deed reference to Robert Blackwell as a merchant from Elizabeth-town. In early 1676 Robert Blackwell left Elizabeth-town and came to New York as a widower with two children whose names were Robert Blackwell, Jr. and Ann Blackwell. There is no record of who Robert Blackwell's wife was, nor any record of the dates or places of birth of these two children Robert and Ann.

Upon his arrival in New York, Robert Blackwell settled, with his two children, in Newtown, Long Island. On March 25, 1676, in contemplation of his marriage to Mary Manningham, daughter of Walter Manningham and step-daughter of Captain John Manning, Robert Blackwell entered a written prenuptual agreement with Mathias Nicolls, the trustee holding title to Manning's Island for Mary Manningham during the life of Captain John Manning. The agreement specified, among other terms, that, in consideration of his marriage to Mary Manningham, Manning's Island would be devised by their wills only to children of Robert and Mary, not to Robert's previous children, and that if Robert and Mary bore no children, title to the island would go to whoever Mary choose, as she would designate in her will.

On April 26, 1676 Robert Blackwell married Mary Manningham and they settled down on Manning's Island, which thereafter was known as Blackwell's Island. Robert and Mary had ten children of their bodies, who they named Bridget, Thomas, Francis, Walter, Henry, Lydia, Sarah, Susannah, Jacob and Mary.

Robert Blackwell's oldest son Robert married Elizabeth Combes, of Newtown, daughter of Francis Combes, a cooper, who died in 1700. Robert removed to Hopewell, New Jersey, where he and Elizabeth raised their seven children named Robert, Francis, Thomas, Jacob, Mary, Ann and Elizabeth. Robert Blackwell died in Hopewell, New Jersey in 1757.

What became of Robert Blackwell and Mary Manningham's daughter Mary is unknown.

It is probably that the four oldest sons of Robert Blackwell and Mary Manningham, namely Thomas, Francis, Walter and Henry, did not survive childhood because there is no further record of them.