Once slated to become a condominium development, this park contains one of the largest tracts of West Indian tropical hardwood hammock in the United States. The park is home to 84 protected species of plants and animals, including wild cotton, mahogany mistletoe, and the American crocodile. Exploring the park?s trails gives visitors a chance to see some of these rare species of plants and animals. Over six miles of nature trails provide a wealth of opportunities for birdwatchers and photographers. Most of the park?s trails are paved and accessible to both bicycles and wheelchairs. Signs along a self-guided nature trail provide information about the park?s ecosystem and wildlife; ranger-guided tours are also available. Located on County Road 905, one-quarter mile north of its intersection with Overseas Highway (U.S. 1).

Florida state parks are open from 8 a.m. until sundown 365 days a year.

A self-guided nature trail winds through the tropical hardwood hammock and includes a native plant butterfly garden. An additional 6 miles of backcountry trails are available to explore simply by completing a backcountry permit at the John Pennekamp Coral Reef State Park Ranger Station. Exploring the trails gives visitors a chance to see some of 84 protected and rare species of plants and animals, including wild cotton, mahogany mistletoe, or the Schaus? swallowtail butterfly. The largest tract of West Indian tropical hardwood hammock in the U.S., contained in this park, also provides a wealth of opportunity for birdwatchers and photographers. The main ?-mile trail is paved and accessible to wheelchairs and bicycles.

Wildlife observation is also outstanding at the park. Northbound in April, and especially while southbound in October, migratory birds are funneled into the Keys by the landform. Many tropical species are resident here, including the white-crowned pigeon, mangrove cuckoo and black-whiskered vireo. Tropical vagrants such as the thick-billed vireo and La Sagra's flycatcher are frequently reported in the park.

Butterfly-watching has rapidly grown in popularity since the mid-1990s; the park features an incredible diversity of species including the Schaus' swallowtail, silver-banded hairstreak, and both hammock and mangrove skippers. Rare tree snails feed on the lichens and bark of the tropical trees, and can be easily observed by park visitors.

The park is named for Dagny Johnson, a local environmental activist, approximately a year before her death in 2003. Through the 1970s, 80s, and 90s, Dagny led the Upper Keys Citizens Association and several other organizations that fought to stop the development that was planned for much of north Key Largo. Preservation of onshore communities was not the only purpose for protecting north Key Largo. The reefs offshore of developed areas in the Keys have been declining rapidly, and those off undeveloped north Key Largo remain in far better condition than most.

Annual Entrance Passes can be purchased at all park ranger stations and museums. If you require immediate use of your pass, this is the best option. Passes can be purchased during regular business hours 365 days a year. Please call the park in advance to ensure availability. Those who are eligible for discounted or free passes may use this method to receive their pass. Annual Entrance Passes may be purchased online by visiting the FLORIDA STATE PARKS ANNUALENTRANCE PASSES web page.