An unlogged and ungrazed ponderosa pine/Douglas-fir landscape in the Colorado Front Range provides critical information for restoring forests in the South Platte watershed. A frame-based model was used to describe the relationship among the four primary patch conditions in the 35-km2 Cheesman Lake landscape:(1) openings,(2) ponderosa pine forest,(3) ponderosa pine/Douglasfir forest, and (4) persistent old growth. Each condition is possible over time at any nonriparian site, with fire and tree recruitment the primary processes causing changes from one condition to another. The Forest Vegetation Simulator model was used to estimate forest conditions at Cheesman Lake in 1900, prior to fire suppression effects. These results and 1896 Cheesman Lake photographs indicate that more than 90 percent of the historical landscape had a crown closure of 30 percent or less, compared with less than 50 percent of current nearby forests affected by logging, grazing, tree planting, and fire suppression. The historical fire regime was mixed severity, and passive crown fire was probably more common than active crown fire. Currently, surrounding forests have almost no openings, little old growth, high tree density, and increased Douglas-fir. Fire behavior has switched to a crown fire regime with sometimes catastrophic results. Historical Cheesman Lake forest landscape conditions are being used to guide restoration of surrounding forests.