I stumbled across a new site last night. The Archives of Maryland Biographical Series is part of the Maryland State Archives website. I found the bio page while searching for Edward Prall [Praul] who served in the Maryland Line from 1776-1783.
The bio page includes a link to the soldier's biography, images, sources and related collections. In this case, some new details arose on "Uncle Ed." One of his sergeants described the fate of his 4th Company at Long Island, including his 2nd Lt. [Prall] being shot in the hand. Prall was one of the officer held on the prison ships near Manhattan.
There have been two dates recorded for Capt. Prall's exchange [he was promoted twice while in captivity]. One was in 1777, the other 1778. A letter, dated 8 April 1778, was included from Brig. Gen. Smallwood to Gen. Washington requesting that he arrange the exchange of 4 officers, including Edward Praul. That would confirm the later date. Edward was released weeks before the Continental Army broke camp at Valley Forge.
Capt. Prall was with the 2st Maryland through 1779. The author of the sketch theorizes that Edward spent most of 1780-81 recruiting in Maryland. [He definitely spent time on recruitment, but details from other soldiers' pensions suggest the captain returned to field service and saw action in the Southern Campaign.]
The article also places his home in Maryland near Churchville.
Another fantastic find!