A signer of that document, though not a delegate.
Personal secretary to President George Washington from 1789 to 1791.
But until Sunday afternoon, if someone had gone looking for his grave at the burial ground, the search would have come up blank.
As blank as the weathered slab that had marked Jackson's resting place for decades.
On Sunday, Christ Church officials dedicated a small plaque at the graves of Jackson and his wife, Elizabeth Willing.
"In grateful remembrance to Major Jackson for his service to this country during the Revolutionary War," it reads, "and to honor his role as Secretary of the United States Constitutional Convention and as the fortieth signer of the Constitution.
"Donated by the caretakers of the Christ Church Burial Ground."
But why now?
"I wanted to do it on a nice day" in a nice month, Hopkins said before the ceremony.
Jackson, who was born in northern England on March 9, 1759, and died Dec. 17, 1828 - neither a gentle month for an outdoor ceremony - was a volunteer in the Second Philadelphia Light Horse troop and later surveyor of customs at the Port of Philadelphia, Hopkins said.
His dedication to duty might best be illustrated by what happened after the document was signed.
"He was assigned to take it to Congress in New York, and presented it to them." Hopkins said.
Washington, he said, headed for City Tavern.