Franklin Falls Dam was built and constructed in 1943 on the Pemigewasset River to protect cities and towns along the Merrimack from flood damage. The operation of the Franklin Falls Dam is different from the operation of other Federal flood control dams in New England for two primary reasons: The dam is built on a major tributary river with the largest upstream watershed of all Federal flood control dams in New England, and the dam has a limited storage capacity (equivalent of 2.8 inches of runoff across the entire watershed) while most Federal dams in New England have between 6 to 8 inches of runoff across their respective, smaller watersheds.

Since the dam has such an enormous watershed and very limited storage capacity by design, it is operated to reduce downstream maximum peak flows and alter the timing of when peak flows impact downstream properties and populations. Since it's conception in 1943, Franklin Falls Dam has prevented more than $165 million in damages.