Google Street View
This marker is located on Monell Avenue at the Southwest corner of the Islip Public Library property.

You can visit it now using Google Street View!
Captain Nathaniel Clock Shown Piloting "Mischief" by Russ Kramer
From the artist's website...
The series was planned as a "best of three" with Atalanta pitted against Mischief (designer: Archibald Cary Smith, 1837-1911, built by Harlan & Hollingsworth of Wilmington, Delaware in 1879 for English owner Joseph Richard Busk of the New York Yacht Club.) Mischief was 3' shorter LOA and LWL, 1' greater in beam, displaced about the same, maybe marginally less, carried 250 sq ft more sail area - rigged with an extra 7' of topmast with a slightly shorter boom (10") and slightly longer bowsprit (1' 8".) Nicknamed "The Iron Pot", she was skippered by Nathanael "Than" Clock during the series. She was arrested for smuggling in 1904, and was finally taken out to sea and scuttled in 1929.
"Mischief" c1881