A small colony of nesting Lesser Snow Geese (Chen caerulescens caerulescens) was discovered on the Ikpikpuk River delta in 1992. The number of nesting pairs averaged 35 (Range = 0–60) from 1992 to 1998, then increased dramatically from 176 in 1999 to 12,373 in 2015, for a λ of 1.40 (SE = 0.138). Concomitant with this dramatic population increase, the geographic extent of the colony expanded annually from three small islands in the northwestern portion of the delta during 1992–1999 to all vegetated deltaic islands in 2001 and farther inland on the mainland from 2006 onward. When colony growth was most rapid (2001–2008), nesting success averaged 79% (Range = 48–97%). Low nesting success during 2009–2014 (< 50% in all years except one), primarily caused by brown bears (Ursus arctos), was followed in 2015 by 96.6% success. In 2015, ∼22,000 adults (in both brood-rearing and adult-only flocks) were accompanied by more than 25,000 goslings in July and August. These numbers represent a remarkable increase in the abundance of Snow Geese west of the Colville River, where only 15 years previously fewer than 500 birds nested. Both immigration and high productivity probably have contributed to colony growth, although the relative importance of effects of the two factors in this growth has not been determined. Further analyses may provide insights into population relationships and the management implications of rapid local and regional growth of Snow Goose populations in northern Alaska.