Florida State Road 666
# Florida State Road 666

State Road 666 (SR 666) is a short state road in Pinellas County. Locally known as Tom Stuart Causeway, Welch Causeway, or Madeira Beach Causeway, the route crosses Boca Ciega Bay from Seminole to Madeira Beach. The bridge crossing Boca Ciega Bay is a bascule bridge with 11 spans, built in 1962. The route ends with an interchange with U.S. Route 19 Alternate (US 19 Alt.) in Bay Pines (originally built for the formerly proposed Pinellas Belt Expressway). The southwestern terminus of the route is at State Road 699 in Madeira Beach, in front of the Ocean Sands hotel.

## Major intersections

The entire route is in Pinellas County.

| Location | mi | km | Destinations | Notes |
| - | - | - | - | - |
| Madeira Beach | 0.000 | 0.000 | SR 699 (Gulf Boulevard) – Redington Beach | |
| Madeira Beach | 0.500– 0.642 | 0.805– 1.033 | Tom Stuart Causeway over Boca Ciega Bay (Gulf Intracoastal Waterway) | Tom Stuart Causeway over Boca Ciega Bay (Gulf Intracoastal Waterway) |
| Madeira Beach | 0.887 | 1.427 | Duhme Road (CR 321 north) | |
| Seminole | 1.2 | 1.9 | Exit to school (EB only) | |
| Seminole | 1.391 | 2.239 | US 19 Alt. (SR 595) – Seminole, Clearwater, St. Petersburg | Interchange |
| 1.000 mi = 1.609 km; 1.000 km = 0.621 mi |||||
