Interesting fella! Thanks for inspiring me to do a little looking into his life.
I thought the article below was a fairly concise summary about Morton and his wife that might provide other FReepers with some basic info.
Good luck on the research!
Anne Justice Morton
1729-1818
Wife of John Morton
When Anne Justis married John Morton in 1745, or 1746, she probably had little idea of the honors the future held in store for her youthful husband, even though he was already looked upon in their little community as a young man with a promising future.
They were of neighboring farmer folk in Chester County, now Delaware County, Pennsylvania. Both were of Swedish extraction, their forebears having been of that tide of immigration which poured into the "lower counties" about the opening of the eighteenth century. John Morton cultivated his own patrimonial acres, but was able to alternate his farm labors with surveying new lands, having been taught that branch of mathematics along with "accompting" by his step-father, John Sketchley, an English gentleman who married the Widow Morton while John was yet an infant in arms. We find nothing more of Anne Justis for .many years. Her husband, grown wealthy, seems to have won the respect and confidence of his neighbours, for he wax commissioned as Justice of the Peace in 1764, and within a few months elected to the Provincial Legislature, of which body he was Speaker for a number of years. Later he was High Sheriff of the county for three years, afterward presiding judge of the Provincial Court, and then one of the judges of the Supreme Court.
During all these years Anne Justis was looking after their estate and rearing their family of children, of whom there were eight, three sons and five daughters. In 1774, Mr. Morton was sent as delegate to the Congress of Colonies in Philadelphia, and was re-elected in 1775 and again in 1776. It was the vote of John Morton, when the delegates of Pennsylvania were equally divided, that broke the tie and threw the voice of the delegation for independence. The labors and responsibilities of his career through this trying period broke down his health, and in April 1777, he died in the fifty-fourth year of his age.
The surviving children of John Morton were as follows: Aaron, the eldest, married Frances, daughter of Richard and Elizabeth Paschall Annitt. They lived in Delaware County for several years and afterward emigrated to Ohio. Sketchley, the second child, became a major in the Pennsylvania line of the Continental Army; he married Rebecca, daughter of John and Mary Neidermar Taylor and died in 1795. Dr. John became a surgeon in the Continental Army and died while a prisoner of war on the British prison ship Falmouth in New York harbor. The late John S. Morton of Springfield had in his possession a letter written by Dr. Morton to his father while he was a prisoner, in which he said they were "almost starved and could eat brickbats if they could get them." He died unmarried. Concerning Sarah and Lydia, nothing definite can be learned. Elizabeth died of consumption, unmarried. Mary married Charles Justis of Kingessing, and Ann, the youngest, married, in 1784, Captain John Davis of Chester County, who had fought through the Revolutionary War as an officer of the Pennsylvania line.
When the British Army passed through the neighborhood of his late residence, after the Battle of Brandywine, they despoiled his widow and children of property to the value of over one thousand dollars. Mr. and Mrs. Morton were members of St. James Church in the town of Chester, and their remains are said to be interred in the old churchyard.
Source: Wives of the Signers: The Women Behind the Declaration of Independence, by Harry Clinton Green and Mary Wolcott Green, A.B. (Aledo, TX: Wallbuilder Press, 1997). Orignaly Published in 1912 as volume 3 of The Pioneer Mothers of America: A Record of the More Notable Women of the Early Days of the Country, and Particularly of the Colonial and Revolutionary Periods (New York: G.P. Putnam's Sons). Pages 192-195. (Some minor spelling changes may have been made.)
You might want to also plan to spend a couple days at local libraries. He resided in Chester which is now Delaware County but was at that time Chester County with the county seat being Media. Check out the courthouse records. A good starting point would be to plan a couple days visiting the local libraries before heading to D.C. These libraries can be a wonderland of genealogical info.
Before you go, make sure you've got all your records in order and have exhausted all internet leads. Remember, don't take anything from the internet or from any other source for fact without actually checking it out yourself - that's the reason for going to the local sources which have the original records.
Just because your aunt didn't have any luck with the park rangers doesn't mean you won't. You have to find just the right one and hope he/she is having a good day. We lucked on to one in Jamestown who let us back into their private archives to research our Dodson line.
Check out the on-line genealogical sites (there are free ones) and correspond with some posters who seem to have a handle on Morton. They might already have the answers your seeking or can give you leads where to locate the original documents.
Another avenue would be to contact the Archives and ask if they would recommend someone who would do some research (for a fee) to try to locate any papers for you before April. This would help save you time and if they did find something you would know exactly where to place your hand on it quickly once you do get there.
He was the salt of the Earth.