The first inhabitants of the area known as Old Bridge, were the Lenni Lenape Indians. They, like many people today, migrated to the shore along the Raritan each summer from their hunting grounds in the north.

When the English gained control from the Dutch in 1664, the state was divided into two provinces, East and West Jersey. In 1682, the general assembly of East Jersey defined the boundaries of Middlesex County as containing all plantations on both sides of the Raritan River, as far as Cheesequake Harbor to the east, then southwest to the Provincial line. This Southwest line is the border of Monmouth and Middlesex Counties and the Township's southern border.

In 1684, South Amboy Township was formed. At that time, it covered an area that now consists of the Townships of Monroe and Old Bridge and the Boroughs of Sayreville and South Amboy.

The forty-two square miles that comprise the Township separated from South Amboy in 1869, and was called Madison Township until 1975, when the name was changed by referendum to the Township of Old Bridge.

The first settlers were John Warne, son of one of the original proprietors of East Jersey, and John and Susannah Brown, who obtained a 1,000 acre land grant from the King of England in 1737. A section of the Township still carries the name Browntown.

Initially, the Township was made up of farms and the population grew slowly. In 1880, the population was 1,662 and in 1950 it had reached only 7,365. Then the building boom started and farms gave way to developments. In 1960, the population was 22,772 and that was only the beginning. The 1980 census sited 51,406 people and even that was questioned because areas of the Township have post offices bearing the names of other communities in the area. Today, the Township population is estimated to be 60,000 and continued growth is forecasted. Of the Township's 38.3 square miles, approximately one third is developed.