Complex sentence: The Ammonoosuc rises on the western slope of Mount Washington, in Sargent's Purchase in the White Mountains of southern Coos County, and flows westwardly into Grafton County, where it turns southwestwardly.
Split into simpler sentences: The Ammonoosuc rises on the western slope of Mount Washington, in Sargent's Purchase in the White Mountains of southern Coos County. Leaving the vicinity of the Presidential Range, the river flows westwardly into Grafton County, where it turns southwestwardly.