Illinois Mountain is a one thousand one hundred twenty-five-foot peak in the town of Lloyd, west of Poughkeepsie, on the southern edge of New York's Catskill region, rising north of nearby Marlboro Mountain. Part of the mountain is preserved as two hundred eighty acres of parkland managed by Scenic Hudson, with hiking trails open across the property. The Town of Lloyd also uses the mountain for reservoirs and other water infrastructure, while the summit area holds a radio tower and additional towers. A gated service road provides access to the top.