 The name of the river, and hence the borough, is thought to come from early explorers who thought that the geography of the area resembled that of the Sadle Burn, the valley surrounding a stream in the Scottish area of Argyll.According to the United States Census Bureau, the borough had a total area of 5.281 square miles (13.680 km2), including 5.261 square miles (13.627 km2) of land and 0.020 square miles (0.053 km2) of water (0.39%).The borough is bisected by the Saddle River, a tributary of the Passaic River.