It's difficult to find more on the topic, the most detail being in 'Portland in the Past' by William Goold (B. Thurston & company, 1886). Here it is related that in the winter of 1812-13 a cartel-ship carrying the flag of truce arrived from Quebec with American prisoners of war for exchange. The ship had docked at Portland due to sickness and a lack of winter clothing. About 25 American soldiers were landed at Portland, and The Argus for 7 Jan 1813 said:
"Dec 24 1812, Arrived cartel ship Regulus seven weeks from Quebec for Boston with 230 prisoners taken at the Battle of Queenstown. Col Scott's regiment, sickly, 26 were too sick to go to Boston in ship - were carried to the hospital on the hill."
The book also related that by Feb 4 (1813), thirteen soldiers had died. Apparently the Regulus waited in harbor for some long period of time before moving on to Boston.
General lay-out of the memorial, with a cobble-stone area marked out by posts (running north-south). At the two extreme ends, grave marker stones are placed for each dead American soldier (at least one was 'unknown'). American flags had been placed at each marker some time previous and remained unmolested. In the center of this area (dark spot) was a large marker boulder with an inscription (shown below).
Within this enclosure
were buried 21 soldiers
captured by the English
at the battle
of Queenston, Canada
in the War of 1812
and died in hospital here
while on their way to
Boston for exchange
Marker stones (Matilda at right for scale!). The stones are all legible, but require maintenance.
To the west of the boulder stands a flag-pole, flying the American flag at full-mast. Homes on the bordering Eastern Promenade can be seen in the distance.
It is a shame that biographies of the 21 American soldiers could not be easily unearthed. The site remains as the coastal land was set aside for recreational use some time afterwards.