I can't help with any information, but for whatever it's worth, Hempstead is in Nassau County, not Queens County, however that is now - I suppose it's possible that back then it was part of Queens County - it's only about 10 miles past the Nassau/Queens border now.
The way the geography works (now - which is all I know about), New York City consists of 5 boroughs - Manhattan, Bronx, Brooklyn, Queens, and Staten Island (also called Richmond). Adjoining the Queens border is Long Island, which consists of Nassau County and beyond that, Suffolk County.