According to the U.S. Census Bureau, the county has a total area of 246 square miles (640 km), of which 230 square miles (600 km) is land and 16 square miles (41 km) (6.5%) is water.
Putnam County is situated in the lower Hudson Valley in the southeastern part of New York, between the Hudson River on its west and the New York-Connecticut border on its east.
Putnam is southeast of Newburgh, and it is north of White Plains. Depending on precise location within the county, road travel distance to New York City ranges between 45 miles (72 km) and 65 miles (105 km).
The terrain of the county is generally hilly. The region of the county nearest the Hudson River is especially so, and is part of the Hudson Highlands. The highest point in Putnam County is Scofield Ridge, with four summits at approximately 1,540 feet (469 m) above sea level. The lowest point is sea level along the Hudson.
The Hudson River, named for Henry Hudson, has provided transportation of goods from New York City, north to the Hudson Valley, throughout history. Between the hills and glacial moraine, Putnam County’s valleys contain numerous wetlands (including part of the Great Swamp), creeks, ponds, lakes (including the 583 acre Lake Mahopac), and reservoirs.
As of 2016 Census estimates, there were 98,900 people and 34,102 households in the county, with 2.84 persons per household. The population density was 432.9 people per square mile (160/km²). 50.1% of the population was female. The racial makeup of the county was 79.6% White alone, not hispanic or Latino, 3.3% Black or African American, 0.4% Native American, 2.3% Asian, 0.1% Pacific Islander, 3.0% from other races, 1.8% from two or more races and 14.3% Hispanic or Latino of any race. 12.6% of the population was foreign born.
4.4% of the population was under the age of 5, 20.5% under the age of 18, and 15.9% were 65 years of age or older. The median age was 43.4 years.
The median income for a household in the county was $97,606, and the per capita income was $41,993. 5.2% of the population was in poverty.
92.7% of the population at least 25 years old had a high school degree or higher, and 38.9% had a bachelor degree or higher.
There were 38,332 housing units, 82.0% of which were owner occupied. The median value of owner-occupied housing units was $354,800.
Putnam County New York neighborhoods include: Barger Street, Indian Hill, Oscawana Heights Rd, Peekskill Hollow Rd, Putnam Valley, Roaring Brook Lake