Chicago Basin comprises the upper portion of the Needle Creek watershed in the Needle Mountains (Colorado), a subrange of the San Juan Mountains in the US State of Colorado. It lies within the Weminuche Wilderness, part of the San Juan National Forest. Needle Creek is an east-side tributary of the Animas River. The basin is a popular destination in summer for climbers and backpackers. The upper portion of the basin is surrounded by three fourteeners: Mount Eolus, Windom Peak, and Sunlight Peak.