Middlefield [Middlesex County] was named in 1744 from the rural part of Middletown. It was incorporated from Middletown in 1866. Area, 13.3 sq. miles. Population, est., 4,107. Voting districts, 2. Principal industries, agriculture and manufacture of cement products, gun sights and gun parts, novelties in plastics, thermometers, hardware specialties, such as wire cutters, tools, dies, fixtures, machinery, and work holding devices.Middlefield includes the village of Rockfall.