Today the blog of the Brooklyn Historical Society has an image of a map of Long Island, circa 1850.
BHS - Map of the Month - January 2014
It is described as a "Travellers Map of Long Island," and was published by J. H. Colton, and there is a link to a citation from New York University Libraries. The resolution isn't too good when enlarge the image, but still, the locations, Flatlands, New Utrecht, Gravesend and others can be made out. I can pick out a road, which I believe would now be Northern Blvd., that skirts just under Flushing, Great Neck, Cow Neck (where I grew up), then Oyster Bay (the village) and Huntington. The road below that (also west to east) would be Jericho Tpk. It goes through Jamaica and Westbury, and continues on to Riverhead.
If you have a fondness for Brooklyn, this is a nice website.