A big mystery looms as to how Franklin Square got its name. Was there a person named Franklin to whom the hamlet paid tribute? Did locals want to establish some connection with the Franklin Square in New York City? Was there perhaps some Benjamin Franklin angle that gave the location its name? No one seems to know for sure. The name origin of Franklin Square's sister hamlet, Washington Square, is less difficult to surmise. Right up the street along what is now Nassau Blvd. was a horse track called the Washington Race Course, roughly where Adelphi University is now located. The nearest settlement to the race course merely borrowed the name of the famed track. But what about Franklin Square?
How about the following theory? -
We know that the streets of Hempstead Village were named in the year 1834. Among the lanes that run north-south through the village, the most central and prominent of them was aptly named Main St. The names chosen by the village elders for the two streets that flank Main St. on either side are Franklin St. to the west and Washington St. to the east.
Why were these names chosen? Here's what I think. During the Revolutionary War and in its aftermath, Hempstead Village was known as a hotbed of British loyalism. Indeed, Tories were dominant in Hempstead and along the South Shore to the extent that this was purportedly the reason for the break off in 1784 of North Hempstead, whose residents generally supported the revolutionary cause, from South Hempstead. The initial years after the war were not kind to those who remained loyal to the British crown, many of whom were forced to leave the US to resettle in New Brunswick or Nova Scotia while others who remained had land confiscated.
By 1834, leaders of Hempstead Village, some of whom no doubt as children and young men were around to live through the hardships endured by Tory families in the post-Revolutionary War era, were eager to shed Hempstead's loyalist legacy and solidify its standing as a patriotic village. As a result, they chose the two most standout heroes of the Federalist cause after whom to name their streets, Benjamin Franklin and George Washington.
From the Beers, Comstock & Cline Long Island map of 1873 - one of the earliest references to the name "Franklin Square".
Back in the 1830s, to the west of Hempstead Village, along the Hempstead-Jamaica road, were two tiny settlements built around the two major cross streets, or "squares", that intersected the road. The first settlement was situated at what is now Nassau Blvd and was originally called Trimming Square, probably informally so on account of the sheep that locals would round up for shearing from the common grazing grounds that was the Hempstead Plains just to the north. At some point in the mid 1800s, the name Trimming square was lost and was replaced by Washington Square, and was named so until the turn of the 20th century when it became known as Munson. The second settlement, a little further west, grew up around the intersection with what is now Franklin Ave and New Hyde Park Rd. This settlement came to be known as Franklin Square. Hempstead Village did not incorporate until 1853, so prior to that the municipal government for the village proper and the greater Town of Hempstead were one and the same.
It's entirely reasonable that at the same time that Hempstead Village designated names for their streets, they likewise chose names for these two squares, and the names they chose paid tribute to the two most prominent national heroes of that time - George Washington and Ben Franklin.