South Bound Brook is a Borough in Somerset County, New Jersey, United States. As of the United States 2000 Census, the borough population was 4,492. What is now South Bound Brook was originally formed as a town within Franklin Township. On March 16, 1869, the name of the community was changed to Bloomington, which lasted until May 29, 1891, when the name reverted back to South Bound Brook town. South Bound Brook was incorporated as an independent borough by an Act of the New Jersey Legislature on April 11, 1907, based on the results of a referendum held on May 1, 1907.