Question: Pigeon Key, Florida is located off an old bridge in which county ?

Context paragraphs:
Old Bridge Airport: Old Bridge Airport (FAA LID: 3N6) is a public-use airport located five nautical miles (9.26 km) south of the central business district of the township of Old Bridge in Middlesex County, New Jersey, United States.  The airport is privately owned.  The airport is located next to Old Bridge Township Raceway Park.  There is 100LL fuel on the field.

Skyway Fishing Pier State Park: Skyway Fishing Pier State Park is a Florida State Park located on the north and south sides of the mouth of Tampa Bay.  When the new Sunshine Skyway Bridge was built on I-275 (US 19) after one part of the old bridge collapsed due to a ship collision, the approaches to the old bridge were turned into the longest fishing pier in the world.  The bridge is lit at night, and the park is open 24 hours a day, 365 days a year.  The most common activity is fishing.  Common catches include snook, tarpon, grouper, black sea bass, Spanish mackerel, king mackerel, cobia, sheepshead, red snapper and flounder.  Snacks, drinks, bait, and fishing supplies can be purchased on the fishing pier, which charges an admission fee of $4.00 per car plus $4.00 per adult, $2.00 per child (6–12 years old) and free, children 5 and younger.

Old Bridge High School: Old Bridge High School (formed from combining the former Cedar Ridge and Madison Central High Schools) is a four-year comprehensive public high school that serves students in ninth through twelfth grades from Old Bridge Township in Middlesex County, New Jersey, United States, operating as the lone secondary school of the Old Bridge Township Public Schools.  The school is located on County Route 516 in Old Bridge Township, however, it is assigned a Matawan mailing address.  The school has been accredited by the Middle States Association of Colleges and Schools Commission on Secondary Schools since 1970, and was most recently re-accredited in 2008.

Seven Mile Bridge: The Seven Mile Bridge is a famous bridge in the Florida Keys, in Monroe County, Florida, United States.  It connects Knight's Key (part of the city of Marathon, Florida) in the Middle Keys to Little Duck Key in the Lower Keys.  Among the longest bridges in existence when it was built, it is part of the Overseas Highway in the Keys, which is part of the 2,369-mile U.S. Route 1.

Pigeon Key: Pigeon Key is a small island containing the historic district of Pigeon Key, Florida.  The 5 acre island is home to 8 buildings on the National Register of Historic Places, some of which remain from its earliest incarnation as a work camp for the Florida East Coast Railway.  Today these buildings serve a variety of purposes, ranging from housing for educational groups to administrative offices for the non-profit Pigeon Key Foundation.  The former Assistant Bridge Tender's House has been converted into a small museum featuring artifacts and images from Pigeon Key's colorful past.  It is located off the old Seven Mile Bridge, at approximately mile marker 45, west of Knight's Key, (city of Marathon in the middle Florida Keys) and just east of Moser Channel, which is the deepest section of the 7 mi span.

Madison Park, New Jersey: Madison Park is an unincorporated community and census-designated place (CDP) located within Old Bridge Township, in Middlesex County, New Jersey, United States.  As of the 2010 United States Census, the CDP's population was 7,144.  The name "Madison Park" reflects Old Bridge's original name of "Madison Township" which it had when it was formed on March 2, 1869 from portions of South Amboy Township, until November 5, 1975, when voters approved a referendum changing the township's name to Old Bridge Township.

Pigeon Key Historic District: The Pigeon Key Historic District is a U.S. historic district (designated as such on March 16, 1990) located on Pigeon Key in Florida.  The district is off U.S. 1 at mile marker 45.  It contains 11 historic buildings and 3 structures.  Although the old Seven Mile Bridge crosses over the island, it and its exit ramp to the island were closed in 2008.  Since then, access has been by ferry or private watercraft only, but in 2014 FDOT approved a $77 million plan to restore it.

East Spotswood, New Jersey: East Spotswood, also known as the settlement of Old Bridge, is an unincorporated community located within East Brunswick, New Jersey and Old Bridge townships in Middlesex County, New Jersey, United States.  The area is made up of homes, businesses, and wetlands for the South River.  The area is located at the junction of New Jersey Route 18, County Route 527 (which is routed along Old Bridge-Englishtown Road, Old Matawan Road, and Old Bridge Turnpike), the western end of CR 516, and the Bordentown and South Amboy Turnpike (CR 615).  The still-active Jamesburg Branch of the former Camden & Amboy Railroad also runs through the community.

Pigeon Key, Florida: Pigeon Key is a historic district located on the small island of Pigeon Key in the lower Florida Keys, United States.  The island is named "Cayo Paloma" on many old Spanish charts.  It is located off the old Seven Mile Bridge, at approximately mile marker 45, west of Knight's Key, (city of Marathon in the middle Florida Keys) and just east of Moser Channel, which is the deepest section of the seven-mile span.

South Old Bridge, New Jersey: South Old Bridge is an unincorporated community located within Old Bridge Township in Middlesex County, New Jersey, United States.  The community consists of homes and businesses between New Jersey Route 18 and County Route 516 in the western portion of the township.  The reason for the odd directional naming is because it is located south of the settlement of Old Bridge (near East Spotswood) while the name of the township of the time was Madison Township.

Supporting paragraphs: Pigeon Key, Florida Seven Mile Bridge
Answer: Monroe County