Calcium is a hamlet in Jefferson County, New York, United States. The population was 3,491 as of the 2010 Census.Calcium is in the Town of Le Ray and was formerly called Sanford's Corner.Historic landmarks include the stone house at the intersection of State Route 342 and County Route 138 that once served as the post office for the area, and the Calcium Community Church at the same intersection. The church was built in 1853 by a group of at least three different denominations, including Methodist Episcopal, Christian, and Unitarian. The building was shared by these and various Christian groups over the years, and remains a community church today.Calcium is located at 44°02′05″N 75°50′32″W / 44.034761°N 75.842114°W / 44.034761; -75.842114.According to the United States Census Bureau, the community has a total area of 5.6 square miles, all land.Calcium is located along U.S. Route 11, south of New York State Route 342, south and west of Fort Drum.