The North Branch of the Westfield River starts at the town of Savoy, Massachusetts in the Berkshires. It flows southeasterly to the town of Cummington where it follows Route 9 to the junction with the Swift River. Here it turns sharply south and flows through the picturesque Pork Barrel region to West Chesterfield. It continues through a wilderness region to the Knightville Reservoir. From here it continues south for about 5 miles to Huntington, Massachusetts where it becomes the main branch of the Westfield River. The Middle Branch and the West Branch join it in this section.