Part of modern-day Route 311 was originally the Philipstown Turnpike, a road built in 1815 to overcome a lack of transportation when the Hudson River froze during the winter months.

The turnpike was a large business center for the county, though it was abandoned due to insufficient tolls to maintain it.

[3] It was created by developers in the early 20th century by damming the Middle Branch of the Croton River,[4] and is one of the few large bodies of water in Putnam County not used as a reservoir by New York City.

At nearly 6,000 acres (2,400 ha), the Great Swamp is the second largest wetland in New York, extending as far north as Dover in Dutchess County.

[9] To resolve the issue, in 1815, the Philipstown Turnpike Company was organized to improve upon a toll road from Cold Spring to the Connecticut border.

By early the next year, a group of engineers led by H. W. Degaff surveyed the region, with the goal of constructing a 16-foot (4.9 m) wide road.

The working crew was composed of Italian immigrants, some of whom were given temporary residence within the Putnam Cigar Factory.

[2][17] In March 1936, a "great and unusual ice flood" caused local water levels to rise.

[20] By 1966, Putnam County's men began drafting into the armed forces to fight in the Vietnam War.

After the Lloyd Lumber Company moved to a larger building along NY 311, the post office occupied the smaller structure; both were situated on the east side of the New York Central tracks.

Residents complained that the new location was inadequate, claiming that parking was insufficient at nearby companies, and that walking along a busy road to reach the post office was dangerous.

After a bidding process to determine the future location, the office was again moved to a former car service station along Front Street.