County Road 5A is Flager Avenue from White Street to Roosevelt Boulevard (SR A1A) in Key West.

[3] Flagler Avenue begins at White Street in Key West and runs northeast.

Continuing east, Flagler Street runs just to the north of Key West International Airport before terminating at Roosevelt Boulevard (SR A1A) just south of US 1 (Overseas Highway).

County Road 905 is Key Largo Drive from US 1 to the Ocean Reef Club near Grayvik.

CR 905 then continues northwest to the Ocean Reef Club on the north end of Key Largo.

In 1944, US 1 was rerouted to its current alignment between Florida City and Key Largo via Jewfish Creek (along the former Overseas Railroad).

After the realignment, the Card Sound Bridge was taken out of service and the route in northern Key Largo eventually became SR 905.

Once across the bridge, it enters Miami-Dade County where it continues as CR 905A to US 1 near Florida City.

When US 1 was rerouted to its current alignment between Florida City and Key Largo via Jewfish Creek (along the former Overseas Railroad), The original Card Sound Bridge was closed to traffic and was later destroyed by a fire.

The western segment was Sombrero Beach Road from the Corte Del Brisas Traffic Circle to US 1 in Marathon.

[citation needed] The eastern segment of CR 931 began at a roundabout with Corte Del Brisas near Sombrero Beach.

[4] The western segment was largely completed in 1960 when the Boot Key Harbor Bridge was built.

[10][11] The state, county, or city of Marathon did not want to finance repairs to the bridge due to the little activity on Boot Key.

From US 1, it heads southeast passing residential streets to the south end of Sugarloaf Key.

A segment of this road is still in service on Upper Sugarloaf Key providing access to Pirate's Cove from US 1.

Perky helped subsidize the construction of the road with Monroe County to connect his town to the Overseas Highway, which at the time ran along present-day CR 939A.

[citation needed] Sugarloaf Boulevard has since been turned over to county control becoming CR 939.

[4] The wooden bridge connecting the original highway to Geiger Key further west was removed in the late 1940s.

[20] In the 1930s, present-day Key Deer Boulevard connected the area of Big Pine Key near the Overseas Railroad with the original Overseas Highway (SR 4A), which ran along present-day Watson Boulevard at the time.

[3] Boca Chica Road begins at the Overseas Highway (US 1) on Big Coppitt Key.

[17][24] Boca Chica Road was later designated SR 941 before becoming CR 941 when it was turned over to county control.