Calling him "an illustrious associate and countryman," "a masterly illustrator of our history," someone with "imminent genius" who was "honorable, brave, sincere, generous," Griswold helped organize a committee that became a veritable who's who of "Who are they??" — mostly-forgotten literary critics and writers: Parke Godwin, Fitz-Greene Halleck, George Pope Morris, James Kirke Paulding, Epes Sargent, Gulian Verplanck and, of course, the ubiquitous Nathaniel Parker Willis.
After a couple delays, the major ceremony was held on February 25, 1852 at Metropolitan Hall on Broadway (it was two years old at the time and would burn down two years later). The main address was given by Daniel Webster, then Secretary of State. Griswold himself held the role of co-secretary in organizing the event, though he may have served as Master of Ceremonies (I haven't seen evidence for this yet).
Remembrance letters were sent by Richard Henry Dana, Ralph Waldo Emerson, Nathaniel Hawthorne, Henry Wadsworth Longfellow, Samuel F. B. Morse, and Francis Parkman (and a whole bunch of obscure folks). Also speaking was Washington Irving, a somewhat controversial selection. Cooper and Irving were recognized early on for being progenitors of American writing, but they were not good friends. Cooper had antagonized Irving, once calling him a "double dealer" with low moral qualities, though Irving himself showed no animosity in return.
Irving later admitted his speech at Cooper's memorial was poorly-delivered. After him spoke William Cullen Bryant, who mentioned "an unhappy coolness" between Irving and Cooper; Irving was hoping that coolness would not come up. Even so, the event was recorded as a success; Elizabeth Oakes Smith was in the audience and, allegedly, was brought to tears. "The whole affair succeeded quite well," recorded Griswold.
Not quite so well, Dr. Griswold.
The committee hoped the event would raise enough money to honor Cooper with a large public statue. They fell short of their goal, raising less than $700. They gave the proceeds to another effort which led to a Cooper monument in Lakewood Cemetery — a marble pillar over 20-feet tall, surmounted by a statue of the author's most famous character, Leather-Stocking (a.k.a. Natty Bumpo).
*The image is from the James Fenimore Cooper Society.