How the system works
Mile markers count down as you drive south. They start at MM 126 in Florida City on the mainland and end at MM 0 in Key West, at the corner of Whitehead and Fleming. The Keys proper begin around MM 106 at Key Largo.
Every business, house, and boat ramp in the Keys is located by its marker: "we're at MM 82, oceanside." Which brings us to the second half of the system.
Oceanside vs. bayside — the only other thing you need
- Oceanside
- The Atlantic side. Driving south, it's on your left. Where the reef is
- Bayside
- Florida Bay and the Gulf, on your right heading south. Where the sunsets and the backcountry are
- Also heard
- "Gulfside" in the Lower Keys, meaning the same thing as bayside
Give a Keys address without the side and you'll be asked for it. It matters — U.S. 1 is often divided, and turning across it isn't always possible.
The drive, marker by marker
Key Largo — MM 106 to 90
- MM 106 — Dagny Johnson Key Largo Hammock Botanical State Park. Rare West Indian hardwood forest.
- MM 102.5 — John Pennekamp Coral Reef State Park, oceanside. America's first underwater park; boats to Christ of the Abyss.
- MM 100 — The African Queen, the restored steam launch from the Bogart film.
- MM 93.6 — Florida Keys Wild Bird Center. Free boardwalks through the mangroves.
Islamorada — MM 90 to 72
- MM 87 — Founders Park. Beach, pool, marina.
- MM 85.5 — Windley Key Fossil Reef Geological State Park. Quarry walls of fossilized coral cut for Flagler's railroad.
- MM 84.5 — Theater of the Sea, operating since 1946.
- MM 82 — Florida Keys History & Discovery Center.
- MM 81.6 — The Hurricane Monument. The 1935 memorial, and the most important ten-minute stop in the Keys.
- MM 78.5 — Boats to Indian Key and Lignumvitae Key, both boat-access only.
- MM 77.5 — Robbie's Marina. Feed the tarpon off the dock.
- MM 73.5 — Anne's Beach. Free, shallow, boardwalk through mangroves.
Long Key to Marathon — MM 70 to 47
- MM 67.5 — Long Key State Park. Undeveloped shoreline and a good paddling trail.
- MM 65 — Long Key Viaduct. The graceful arched railroad span that appeared on the railway's own posters.
- MM 59 — Dolphin Research Center, Grassy Key.
- MM 53 — Florida Keys Aquarium Encounters.
- MM 50.5 — Crane Point. Hammock trails, museums, and a 1900s Bahamian house.
- MM 50 — Sombrero Beach. The best free beach in the Middle Keys.
- MM 48.5 — The Turtle Hospital. Book ahead.
- MM 47 — The Old Seven Mile Bridge. Walk or cycle out over open water.
- MM 45 — Pigeon Key, beneath the old bridge. The railroad workers' village.
The Lower Keys — MM 40 to 9
- MM 37 — Bahia Honda State Park. The best sand beach in the Keys, beneath the ruined rail bridge.
- MM 33 — Big Pine Key. Key deer country; watch your speed, especially at dusk.
- MM 30.5 — Key Deer Refuge headquarters; Blue Hole and the nature trails are up Key Deer Boulevard.
- MM 27 — Ramrod Key, jumping-off point for Looe Key Reef.
- MM 17 — Sugarloaf Key. Site of the Perky Bat Tower, a 1929 mosquito-control folly.
- MM 10–5 — Big Coppitt and Boca Chica; the naval air station and the last of the flats.
Key West — MM 4 to 0
- MM 4 — Stock Island. The working waterfront: commercial fishing fleet, boatyards, and increasingly the good, cheaper restaurants.
- MM 1 — Old Town begins. Park and walk from here.
- MM 0 — Whitehead and Fleming. The end of U.S. 1, which runs from this corner to the Canadian border in Maine.
Driving it: what nobody tells you
- It takes longer than the map says. Miami to Key West is about 3.5 hours with no stops and no traffic. Both of those conditions are rare. Give it four to five, more on a weekend.
- Most of it is two lanes. Long stretches have no passing. You will end up behind someone doing 40 in a 55, and there is nothing to be done about it. This is a feature of the Keys, not a bug.
- Southbound Friday and northbound Sunday are the two heaviest patterns, driven by Miami weekenders. Travel against them if you can.
- Fill the tank in Homestead or Florida City. Gas gets more expensive with every mile marker you pass.
- The 18-Mile Stretch from Florida City to Key Largo is a single dead-straight road across the marsh with a barrier down the middle. It is heavily patrolled. Don't.
- Sunset driving southwest puts the sun directly in your eyes on the bayside stretches. Sunglasses are a safety item here.
- The bridges are the reward. Seven Mile, Bahia Honda, Long Key. If you can, drive it once in early morning light with the windows down.
Why the markers exist at all
They're a leftover from the railroad. Flagler's Overseas Railroad measured its way down the islands, and when the 1935 hurricane ended the trains and the state converted the bridges to carry cars, the mileage system came with them.
So every time you tell someone you're staying at MM 82, you're using a hundred-and-twenty-year-old railroad surveyor's measurement. That's the Keys in one detail: nothing here is ever entirely new, and the old thing usually still works.