Nipmuck State Forest and Bigelow Hollow State Park in the town of Union lie within one of the largest unbroken forest areas in Eastern Connecticut. Nipmuck is the second oldest state forest in Connecticut. The first parcel was acquired in 1905. Additional lands in the towns of Stafford, Ashford, Willington, and Woodstock have been added to the forest over the years. Today Nipmuck State Forest and Bigelow Hollow total over 9,000 acres. The recreation area in Bigelow Hollow was established in 1949 by the State Park and Forest Commission.

The name "Bigelow" is a mystery since no person of that name seems to have been associated with this area. According to older residents of Union, the name is derived from "Big Low" in reference to the deep hollow in which the 18-acre pond of that name is located. The word "Mashapaug" is the Nipmuck Indian word for "Great Pond". The present lake of 300 acres was originally about half the size. In the mid-1880's, two different parties attempted to draw the water from this natural pond. One party ditched to the north and the other to the south. The latter party was forced to give up the battle when they ran into a ledge and later joined forces with their rivals to create the present lake. Two other smaller ponds, Breakneck and Griggs, lie to the north and east of Mashapaug in Nipmuck State Forest.

The contrast of rock, water, and mixed deciduous/evergreen woodland provide ample beauty to the many visitors this park receives.