The East Troublesome Fire, the second largest wildfire in Colorado history, was first reported on October 14, 2020, northeast of Kremmling and burned eastward for about two weeks. Its most rapid growth began on October 21, 2020, when it expanded from 18,550 acres to 187,964 acres in less than 24 hours, entered Rocky Mountain National Park on the west side near Grand Lake, crossed the Continental Divide, and encroached on Estes Park. A winter storm with cold temperatures, lighter winds, and snow greatly reduced its spread, and it was fully contained at the end of November. The fire burned 193,812 acres, including 21,307 acres within Rocky Mountain National Park, damaging wildlife habitat and soil, and its full effects on natural resources remained unknown pending further research. An estimated 580 structures were destroyed or damaged, including within the park the entrance station office, a vault toilet, the 95 year old Fern Lake Cabin, and historic structures in the Green Mountain housing area, including the Onahu Lodge. In November 2020, a National Park Service Burned Area Emergency Response team assessed post-fire threats within Rocky Mountain National Park, including flooding, debris flows, and impacts to vegetation, wildlife, historic properties, and recreation infrastructure, as a step toward recovery. Although many trees and some animals were lost and recovery may take a long time, fire can also open space, enrich soil, increase sunlight, and support new plant growth, helping keep Rocky's forests healthy and increasing biodiversity.