The upper Delaware River basin in New York is characterized by three widely different modes of deglaciation. Ice in the West Branch Delaware River basin stagnated in a series of six zones, each ranging in length from 16 to 24 km. Each zone contains three or four outwash-kame–moraine-kame terrace morphologic sequences. The location of the sequences within a zone was controlled by deposition from tributary streams. In contrast, the East Branch Delaware River was the site of three successive glacial-lake levels, each controlled by a till dam. Deposition into these lakes was in the form of kame deltas. Deglaciation to the south in the valleys of the Beaver Kill and Willowemoc Creek was by mass stagnation. These highly contrasting styles of deglaciation help to account for the problems in tracing ice margins across the Catskill Mountains.