Harper Lake

Harper Lake is a pristine one-mile loop trail and fishing destination in Louisville, Colorado, with sweeping views of the Front Range that make sunrise and sunset visits genuinely memorable. If you live in Boulder County and want a quick, easy walk around a clean lake with mountain views, reliable fishing, and a calm atmosphere, Harper Lake consistently delivers without the crowds you would find at nearby Walden Ponds or Boulder Reservoir.

The lake sits within a residential area of Louisville and doubles as a municipal drinking water reservoir for the City of Louisville, which stores water from South Boulder Creek across several locations including Harper Lake, Marshall Lake, and Louisville Reservoir. Because the lake serves as part of the city water supply, swimming, wading, and any bodily contact with the water is strictly prohibited. Dogs are also not permitted anywhere around the lake, as the surrounding area is classified as a wildlife sanctuary.

The trail that circles Harper Lake is exactly one mile and sits on a flat, well-maintained path that works for walkers, joggers, and casual cyclists. The loop is popular with morning runners, families with strollers, and retirees who appreciate the level terrain and open sightlines. A connecting underpass leads to the Davidson Mesa trailhead, which opens up longer hiking and biking routes for those who want to extend their outing. Harper Lake is also part of the Lake to Lake Trail, which connects Davidson Mesa to Waneka Lake, providing a multi-mile corridor through Louisville's open space network.

Fishing at Harper Lake is productive and accessible from several points along the shoreline. The lake holds rainbow trout, largemouth bass, and channel catfish, with the best action between May and October when water temperatures sit between 50 and 80 degrees. A boat permit is required for anyone 12 or older who wants to paddle on the lake, and permits are sold online through the City of Louisville from April 1 through September 30 each year. Only manually portable boats are allowed — canoes, kayaks, rowboats, paddleboats, and inflatable boats are permitted, but paddleboards are not. No motorized boats or trailers are allowed.

The trailhead has adequate parking and a small restroom near the entrance. There is no shade along the trail, so midday summer visits can feel hot. Spring and fall provide the most comfortable walking conditions, and winter visits offer quiet solitude with crisp views of the snow-capped Continental Divide.

Harper Lake is one of those places that regulars describe as never disappointing. The teal-colored water in spring, goslings following geese along the shore, and the mountain panorama at golden hour create a setting that punches well above its modest size. It is a dependable, low-effort destination for anyone in the Louisville, Superior, or south Boulder area who wants a quality outdoor experience close to home.