I hope to soon post a piece I am working on about Dr. Gregg and Dr. John Emerson, owner of Dred Scott. Gregg was summoned by Emerson when the latter was dying in 1843 in Davenport. Gregg witnessed Emerson's will at the LeClaire Hotel, where Emerson and his wife and child were living while they built a brick house close by. The Irish background of the two doctors was remarkably similar. They also crossed paths as Emerson was leaving the rotting Fort Armstrong for Fort Snelling and Gregg was arriving in Rock Island in the spring of 1836.
In 1951 the Rock Island Medical Society published a 50 year history. It was dedicated to Dr. Patrick Gregg, though it does not contain much info about him.
In 1879 John Gregg, the drill master and Patrick's son, was indicted and convicted of embezzling money from the U S Post Office in Chicago. I will post the details when I organize them. John was pardoned by Rutherford B Hays and went on to live a successful life. He may have taken a hit for his brother in law General John McArthur, the post master, who was also indicted, convicted and pardoned. John transferred from the 12th Illinois that had been formed by McArthur in the summer of 1861 to Patrick Gregg's company of the 58th in December of 1861 by order of General Halleck. After being a POW John became McArthur's aide-de-camp. Some of John's old 12th comrades were also captured at Shiloh.
McArthur was a competent Brigade commander who was stellar at Nashville.