On the corner that the Morbid Anatomy Museum now occupies, there was once a plaque marking the intersection as the "Burial place of ye 256 Maryland soldiers who fell in ye combat at ye Cortelyou House on ye 27th day of August 1776." If Wikipedia is to be believed, these soldiers were part of the Maryland Regiment, who were termed "immortals" due to their bravery, and nicknamed "The Dandy Fifth" because they came so fancily equipped.
More on the regiment and the battle, also from Wikipedia:
The Maryland Regiment had joined the Continental Army barely two weeks before the Battle of Long Island. Unlike most of Washington's Army, the Maryland contingent had been well drilled at home and were so well equipped – they even had bayonets, a rarity for the Army – that the Regiment was known at home as the Dandy Fifth, and to the rest of the Army as "macaronis", the then current word for dandies...
The bravery of the Maryland Regiment earned them the name "immortals". The dead were buried in a mass grave consisting of six trenches in a farm field. The gravesite is located on what is now Third Avenue between 7th and 8th Streets. Until the widening of Third Avenue in 1910, the site was marked by a tablet that read: "Burial place of ye 256 Maryland soldiers who fell in ye combat at ye Cortelyou House on ye 27th day of August 1776." The result of the brief battle was stunning for the Americans. More than a thousand men were killed, captured, or missing. Generals Stirling and Sullivan were in the enemy's hands. The battalion had lost more than 250 of their number. Most of the Marylanders' casualties occurred in the retreat and desperate covering action at the Cortelyou House. Ultimately, of the original Maryland 400 muster, 96 returned, with only 35 fit for duty.
Historian, Thomas Field, writing in 1869, "The Battle of Long Island," called the stand of the Marylanders "an hour more precious to liberty than any other in history." Four companies of the 1st Maryland stood as the final anchor of the crumbled American front line, and their heroic action not only saved many of their fellows but afforded Washington critical respite to regroup and withdraw his battered troops to Manhattan and continue the struggle for independence.
Source: The Battle of Brooklyn 1776 by John J. Gallagher (Sarpedon Publishers, 1995)
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Thanks, Movie Mike, for bringing this to our attention!