Florida State Road 666

State Road 666
State Road 666
Tom Stuart Causeway / 150th Avenue
Route information
	Maintained by FDOT
Length	1.391 mi (2.239 km)
Major junctions
West end	SR 699 in Madeira Beach
East end	; US 19 Alt. in Seminole
Location
Country	United States
State	Florida
County	Pinellas
Highway system
	Florida State Highway System; Interstate; US; State Former; Pre‑1945; ; Toll; Scenic;

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^[1]	km	Destinations	Notes
Madeira Beach	0.000	0.000	SR 699 (Gulf Boulevard) – Redington Beach
	0.500– 0.642	0.805– 1.033	Tom Stuart Causeway over Boca Ciega Bay (Gulf Intracoastal Waterway)
	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