The settlers were attacked when they ventured far from their palisade, and the Pequot destroyed their provisions and burned warehouses while they attempted to interrupt river traffic to Windsor, Wethersfield, and Hartford.

[5] During the Siege and Battle of Saybrook Fort, the Pequot and New England colonists assessed each other's military capabilities, and adjusted countertactics.

Lessons learned during the siege of Saybrook escalated the Pequot War in Connecticut Colony, and indirectly resulted in the attack and destruction of Mistick Fort[6] (May 1637).

The seal was brought from England by Colonel George Fenwick, and depicted 15 grapevines and a hand in the upper left corner with a scroll reading "Qui Transtulit Sustinet", "He who transplanted sustains".

In 1647 Major John Mason assumed command of Saybrook (Colony) Fort, which controlled the main trade and supply route to the upper river valley.

He spent the next 12 years there and also served as commissioner of the United Colonies, the chief military officer, magistrate, and peacekeeper.

In 1659, almost all settlers from Saybrook under the leadership of Mason, purchased land from Uncas, sachem of the Mohegan tribe, removed to and founded Norwich, Connecticut.

[7] This second fort was eventually abandoned after 200 years and the battery mound remained until 1871, when the Valley Railroad leveled it and other hills on the point to provide needed fill for their tracks across the north and south coves.

In 1661, a witch trial was held of Saybrook residents Margaret Jennings and her husband Nicholas, who were accused of causing the deaths of Marie Marvin and others.

In early 2007, plans were established to return the former town hall building to its original use as a theater.

A committee was attempting to raise another $2.5 million, partly for the renovation and to add two wings, but also for an endowment.

[10] According to the United States Census Bureau, the town has a total area of 21.6 square miles (56.0 km2), of which 6.6 sq mi (17.0 km2) (30.45%) are covered by water.

Coastal Connecticut (including Old Saybrook) is the broad transition zone where so-called "subtropical indicator" plants and other broadleaf evergreens can successfully be cultivated.

Old Saybrook averages about 90 days annually with freeze (temperatures of 32 °F/0 °C) – about the same as Baltimore, Maryland, or Albuquerque, New Mexico, for example.

Amtrak, the national rail passenger system, provides daily service along the Northeast Corridor to Boston, New York, and points south.

The high-speed Acela Express passes through Old Saybrook, but does not stop; service is provided by the conventional Northeast Regional.

Interstate 95 runs across the town from west to east (though it is signed north–south), and connects Old Saybrook to New Haven and New London along the Connecticut shoreline.

Connecticut Route 9 has its southern terminus at I-95, and extends to the northwest to ultimately reach Middletown and Hartford.