The Palmer Divide is a ridge in central Colorado that separates the Arkansas River basin from the Missouri River (via the Platte River) basin. It extends from the Front Range of the Rockies in central Colorado, eastward toward the town of Limon. The western end of the Palmer Divide is generally considered to be at Palmer Lake, located south of Denver and north of Colorado Springs. However, the divide between the two river basins actually extends west and then north to a junction with the Continental Divide at McNamee Peak.
The Palmer Divide is named after William Jackson Palmer, the founder of Colorado Springs. For much of its length, it travels very roughly along the northern border of El Paso County. Thus, it forms a natural separator between the Denver and Colorado Springs metropolitan areas. The elevation along the divide varies between about 6,000 and 7,887 feet, with the high point being Bald Mountain in southern Douglas County. This peak can be seen from I-25 just northeast of Monument Hill.
This uplifted area causes a slight increase in precipitation from the rest of eastern Colorado, resulting in the presence of the Black Forest, a peninsula of trees surrounded by dryer grassland plains.
This terrain feature is the cause of several small scale, or microscale, weather patterns, and it can make a great difference in the weather between Denver and Colorado Springs. Although the elevation technically qualifies it for the foothills category, it does not parallel a mountain chain as foothills generally do; instead, the Palmer Divide is perpendicular to the main chain of mountains. Due to the orientation of the Palmer Divide with respect to the eastern plains, the weather can be similar to that of the foothills during active weather with enhanced precipitation, especially during snowstorms. Cities and towns near the Palmer Divide include Castle Rock, Parker, Franktown, Elizabeth, Kiowa, Monument, Elbert, Black Forest, Sedalia, Palmer Lake, and northern communities of Colorado Springs, such as Gleneagle and Briargate.