Part of the Overseas Heritage Trail and almost entirely inside Curry Hammock State Park, the Grassy Key Trail is a 4.4 mile linear paved path under the power lines between Marathon and Grassy Key.
It is hemmed in by tropical forest as it passes through the state park. At the northern end, there are expansive views of the tidal rock barrens surrounded by mangrove forest.
Our resources for exploring the area
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Location: Grassy Key, Marathon
Length: 6 mile round-trip
Trailhead: 24.7413, -80.9972
Restroom: inside Curry Hammock State Park (fee for entry)
Land Manager: Florida State Parks
Be very cautious of poisonwood trees along the path, as there are many in evidence. Lean your bike against signposts or benches (or use the provided bike racks) instead of against tree trunks. Put on bug spray if you plan to make any stops.
There are several options for parking to ride or walk this trail. We recommend this as a bike ride as shade is almost non-existent and the mosquitoes can be very, very bad. The best bet for cyclists is to use the Grassy Key trailhead along US 1 south of the state park’s main entrance, as access to it is free. If you are camping at the state park or enjoying the day use facilities, you can cycle out of the park and cross US 1 to meet the trail on the bay side.
If you want to start your ride farther south along US 1 to add on another 2.6 miles round-trip (total of 8.6 miles), park at the large bayside parking area on Marathon that adjoins the Overseas Heritage Trail. That route extension is shown in darker blue on the trail map. Unlike the rest of the route, it stays within view of US 1 for the 1.3 miles between the two trailheads.
Leave the Grassy Key trailhead and head north along the paved path. It sits under the power lines, so there is no shade to speak of. It’s a straight line off into the distance.
However, the saving grace of this trail is the screen of tropical forest between it and US 1, which helps muffle road noise and makes for a nicer view.
A small rest stop sits next to the trail. Stop here to see the overview map and, on the back of the kiosk, information about habitats you’ll see along this route.
Pass the turnoff for the beginning of the Curry Hammock Nature Trail at a kiosk on the left. You’ll pass a limerock road on the right, as well.
Cross a paved road across US 1 from the main entrance to Curry Hammock State Park.
By 1.3 miles, the tidal rock barren on the bay side has been taken over by invasive species like Australian pine.
The rocks are white and chalky, with some interspersed mangroves and bay cedar. Pass by a power substation with a limerock road leading to it.
At 2.5 miles, Cross Kyle Avenue. It leads back to some homes. The trail curves soon after.
There is a bench and a place to walk down into the tidal rock barren for views across the mangrove-lined salt ponds. The mangroves are pretty roughed up after Hurricane Irma.
Trail’s end is at Guava Avenue at 3 miles. It’s here that the Bike Route sign directs you out into traffic to cross US 1 to use the bike lane to continue north along the Overseas Heritage Trail route. Turn around here and head back to the trailhead.
Learn more about Curry Hammock State Park & the Overseas Heritage Trail
Bring your binoculars for fall birding at Curry Hammock State Park, where migrating raptors cruise overhead by the hundreds following a major flyover route.
See our photos of the Grassy Key Trail
More worth exploring while you’re in this area.
Part native, part cultivated, Crane Point Hammock is 63 acres of tropical hardwood hammock in the heart of Marathon. Preserved from development in 1989 by the Florida Keys Land Trust, it is the largest tropical hammock in the Middle Keys.
At the southern tip of Marathon, Sombrero Beach offers beachgoers a natural strand and an easy beach walk within sight of the Keys’ largest lighthouse.
Spanning shore to shore across much of its namesake island, Long Key State Park offers a bounty of botanical wonders across a variety of rare Florida Keys habitats.