If you carefully keep your bird records by county, be sure to use the specific hotspots in this area so that the birds will be assigned to the proper county. The Hampden-Hampshire county line is in the middle of the Connecticut River.Birds reported on checklists for this hotspot are assigned to Hampden County.

The Holyoke Dam is a historic structure that harnesses the power of the Connecticut River in Massachusetts. It was built in 1900 to replace two earlier timber dams that failed. The dam is made of granite and is 30 feet high and 1,020 feet long. It diverts water from the river into the Holyoke Canal System, which provides hydroelectric energy to the city of Holyoke and its industries. 

The current dam is the third structure to be built across the Great Falls at South Hadley. The dam, along with the Canal System and its Testing Flume, is recognized by the American Society of Mechanical Engineers as a Historic Mechanical Engineering Landmark for its use by Clemens Herschel in the development of the Venturi meter, the first means of measuring large-scale flows, and the McCormick-Holyoke Turbine by John B. McCormick, also known as the Hercules Turbine, which doubled the efficiency of turbines to more than 80% in its time.