Dagny Johnson Key Largo Hammock Botanical State Park, Botanical state park in Key Largo, Florida, US.

Dagny Johnson Key Largo Hammock Botanical State Park is a protected natural area in Key Largo, Florida, containing one of the largest surviving tropical hardwood hammocks in the continental United States. Walking trails wind under a dense canopy where many native tree species grow close together.

The land was slated for a large residential development in the 1970s before conservationists pushed back and the area became a protected state park in 1982. It was named after Dagny Johnson, an activist who spent years campaigning to keep this land undeveloped.

Along the trails, small signs name the native trees, shrubs, and animals that share this patch of tropical forest. Visitors often slow down to read them, which gives the walk a different rhythm than a typical nature hike.

The park entrance is on County Road 905, a quarter mile north of its junction with US-1. A one-kilometer paved path and about nine kilometers of trails start from the main path, which has self-guiding signs. Ranger-led tours are offered. The park is open from 8 a.m. to sundown; bring closed shoes and water.

The Key Largo woodrat and the Key Largo cotton mouse live only in this part of Key Largo, and 90% of their habitat lies within this park and the adjoining Crocodile Lake National Wildlife Refuge. The park also shelters 84 protected species, including the American crocodile and the island swallowtail butterfly.