State Road 21 | ||||
|---|---|---|---|---|
| Blanding Boulevard | ||||
 SR 21 highlighted in red | ||||
| Route information | ||||
| Maintained by FDOT | ||||
| Length | 57.573 mi[1] (92.655 km) | |||
| Existed | 1945–present | |||
| Major junctions | ||||
| South end |  SR 20 near McMeekin | |||
 SR 26 in Melrose SR 100 in Keystone Heights SR 224 near Orange Park I-295 in Jacksonville | ||||
| North end |  US 17 in Jacksonville | |||
| Location | ||||
| Country | United States | |||
| State | Florida | |||
| Counties | Putnam, Bradford, Clay, Duval | |||
| Highway system | ||||
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State Road 21 (SR 21) runs mostly in a southwest-to-northeast direction in the US state of Florida from McMeekin to Jacksonville. It is also known as Blanding Boulevard for much of its length.
SR 21 is one of three routes, along with Roosevelt Boulevard (US 17) and the First Coast Expressway (SR 23), that connect Jacksonville with its surroundings west of the St. Johns River. Congestion has become a problem over the years as local government works to develop infrastructure for the growing populations of Orange Park, Middleburg and Green Cove Springs with the northern connectivity sought and thought to be achieved by drastic road widening despite the decimation of Lake Shore's prewar scale. Residents of both Clay and St. Johns counties' communities rely on Duval's economy (Jacksonville) for employment. As a result, traffic is heavy during morning and evening rush hour, especially near and on I-295. Such has spurred the creation of the Collins Road / I-295 interchange.
Blanding Boulevard was named after Albert Hazen Blanding (November 9, 1876 – December 26, 1970) who was a United States Army General. He was one of the most distinguished military figures in Florida's history.