New York Museums active in 1868;

Two that come to mind are the New-York Historial Society - founded 1804 and
the National Academy of Design - founded 1826.  Both have art collections.
Either one is a good candidate to have purchased the painting.

The New -York Historical Society is the oldest of all the American museums.
Both of these are still in existance.  There may have been others but none
come to mind.  The Metropolitan Museum of Art didn't start till 1870.

If you need addresses or phone nembers let me know.

Jim Maguire