[2] The river's headwaters are at Byram Lake in Westchester County, New York, at an elevation of 750 feet (230 m), and flow southward, crossing the New York-Connecticut border and eventually flowing into Long Island Sound at Port Chester Harbor.

Several bridges cross the river, as well as several dams controlled by the Town of Greenwich, Connecticut.

[2] The Byram River was once a center of economic activity where shipbuilding and fishing were major industries.

On April 15, 2007, a nor'easter flooded areas near the river on both the Connecticut and New York sides.

[2] As of the summer of 2007, three of these in northwest Greenwich had been identified by state inspectors as in critical need of repair, and all were scheduled for work:[3]