Back in the early 1800s Brooklyn was it's own city. It existed within Kings County and was separate from New York City. Now of course, it is a boro of NYC.
In an effort to meet their quickly growing population, Brooklyn's infrastructure was going beyond it's own city line. By the mid 1800s Brooklyn had great demand for more water. The solution was to take water from lakes and streams further east on Long Island.
A reservoir was set up in Ridgewood, Queens. As the need for more water increased, Brooklyn would source water further east. This is were places in Queens such as the Aqueduct Race Track and Conduit Blvd. got their names. Eventually the underground conduit reached all the way to Freeport, then even further to Wantagh and Massapequa.
Back then Nassau County didn't exist and was part of Queens County. It was in 1891 when the Brooklyn Water Works Millburn pumping station was opened. It lies in Freeport and served the purpose of pumping water from nearby water sources such as Millburn Creek to its south. It was a large Romanesque style building. In 1898 Brooklyn became part of New York City. A year later part of Queens followed. The other part becoming what is today Nassau County. This allowed Brooklyn to source water from NYC's supply which was brought from upstate reservoirs via the Croton Aqueduct.
Form 1929 until 1977 the Millburn pumping station remained operational as a standby water source for emergencies. In 1977 the three steam powered pumps were removed along with all the other machinery. By 1989 a developer wanted to turn it into condos. That deal was never realized, however the Water Works in Freeport is showing its age. The roof is gone for the most part and some walls are missing. However the way it has deteriorated makes it look even more Romanesque now more than ever. As for the Wantagh and Massapequa pump houses, they are still around too.