Weminuche Wilderness, Colorado. Backpacking near Highland Mary Lakes in the Weminuche Wilderness in the San Juan Mountains of Colorado. As Colorado’s largest officially-designated wilderness area at 488,210 acres, the Weminuche includes the heart of the rugged San Juan Mountains and contains 3 summits over 14,000 feet. The late-summer monsoon drenches these rugged mountains with downpours every afternoon with accompanying spectacular displays of wildflowers.