KittyNY, if I'm reading the map correctly, it would appear that Reeves Park is in Baiting Hollow ("Riverhead, NY 11901" mailing address).
The geography of Baiting Hollow is confusing because Baiting Hollow is one of those many villages and hamlets on Long Island where none of the places in the community have the hamlet name as part of their mailing address.
For those who may not be familiar with Baiting Hollow:
Baiting Hollow is a hamlet (an unincorporated area) in the north-central part of the Town of Riverhead, in the northeast part of Suffolk County.
Beginning on the north and moving in a clockwise direction, the Hamlet of Baiting Hollow in the Town of Riverhead is bordered on the north by Long Island Sound; on the east by the Hamlet of Riverhead; on the south by the Hamlet of Riverhead and the Hamlet of Calverton; and, on the west by the Hamlet of Wading River.
Baiting Hollow is one of those many villages and hamlets on Long Island where none of the places in the community have the hamlet name as part of their mailing address: places in the Hamlet of Baiting Hollow have a "Calverton, NY 11903" and "Riverhead, NY 11901" mailing address.
For a good set of town-by-town maps showing all the villages and hamlets in each of LI's 13 towns (3 in Nassau County and 10 in Suffolk County): Excellent Long Island Geographic Resource