Deep River [Middlesex County] was formerly known as Saybrook, a fort then a settlement in 1639. It was named from Lord Say & Sele, and Baron Brook. Its Native American name is "Pattaquasset".Area, 14.2 sq. miles. Population, est., 4,461. Voting Districts, 1. Principal industries, agriculture and manufacture of plax and plastic goods, electric soldering irons, business forms.