Route 1A is a numbered state highway

State highway

State highway, state road or state route can refer to one of three related concepts, two of them related to a state or provincial government in a country that is divided into states or provinces :#A...

 in Rhode Island

Rhode Island

The state of Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a state in the New England region of the United States. It is the smallest U.S. state by area...

, running 34.4 miles (55.4 km) in five sections.

Route

Route 1A follows U.S. 1

U.S. Route 1 in Rhode Island

In the U.S. state of Rhode Island, U.S. Route 1 is a major north–south state highway through Providence. Staying close to the Atlantic Ocean and Narragansett Bay, it is a longer route than Interstate 95, and many portions are a four-lane divided highway....

 closely through South County

Washington County, Rhode Island

Washington County, commonly known colloquially as South County, is a county located in the southwestern part of the U.S. state of Rhode Island. Washington County borders Kent County to the north, New London County in Connecticut to the west, Suffolk County in New York to the southwest, the Atlantic...

. It can be separated into five sections:

• The first section (8.8 miles in length) begins as US-1 crosses the Pawcatuck River into Westerly, Rhode Island. From US-1, it turns south along Main St, before bearing left onto Beach Street. It then turns south onto Watch Hill Road before turning south and east along Shore Road, until Shore Road meets Post Road not far from the Charlestown
  Charlestown, Rhode Island
  Charlestown is a town in Washington County, Rhode Island, United States. The population was 7,827 at the 2010 census.-History:Charlestown is named after King Charles II, and was incorporated in 1738. The area was formerly part of the town of Westerly...
  
   town line. Many maps incorrectly post the entire length of Watch Hill Road west of Shore Road as Route 1A. The road serves as a beach bypass, coming close to Misquamicut State Beach, East Beach, Atlantic Beach and Watch Hill.

• The second section (1.3 miles in length) follows the Old Post Road route in Charlestown past Ninigret State Park before merging back (briefly) with US-1.

• The third section (3.1 miles in length) begins less than seven hundred feet after RI-1A becomes concurrent with US-1. It again follows Old Post Road through Charlestown and into South Kingstown
  South Kingstown, Rhode Island
  South Kingstown is a town in Washington County, Rhode Island, United States. The population was 30,639 at the 2010 census.South Kingstown includes the villages of Kingston, West Kingston, Wakefield, Peace Dale, Snug Harbor, Tuckertown, East Matunuck, Matunuck, Green Hill, and Perryville. Peace...
  
   before re-merging with US-1. It serves again as a beach traffic bypass, granting access to the roads to East Beach State Beach, Charlestown Town Beach and Green Hill Beach.

• The fourth section (2.4 miles in length) follows Post Road again, north of US-1. The route, while bypassing the busier US-1, is little more than a residential road. It is also the only segment which is actually north of US-1.

After the fourth section, RI-1A is concurrent with US-1 for over five miles (8 km) through South Kingstown and a short portion of Narragansett

Narragansett, Rhode Island

Narragansett is a town in Washington County, Rhode Island, United States. The population was 15,868 at the 2010 census, but there is a greater population in the summer. The nickname for the town is "Gansett". The town of Narragansett occupies a narrow strip of land running along the eastern bank...

. It unofficially leaves the route and re-emerges at the Narragansett rotary.

• The fifth section (12.7 miles in length) begins at the Narragansett roatary. It follows Kingstown Road to Beach Street at the Narragansett Town Beach, not far from the famous Coast Guard House. It then turns onto Boston Neck Road, crossing the Pettaquamscott River and heading into Narragansett's business district. It then crosses into the Saunderstown
  Saunderstown, Rhode Island
  Saunderstown is a small village and historic district in the towns of Narragansett and North Kingstown in Washington County, Rhode Island, United States....
  
   neighborhood of North Kingstown
  North Kingstown, Rhode Island
  North Kingstown is a town in Washington County, Rhode Island, United States. The population was 26,486 at the 2010 census. The famous American portraitist Gilbert Stuart was born in the village of Saunderstown, located in the southern region of North Kingstown....
  
  , before passing over Rhode Island Route 138
  Rhode Island Route 138
  Route 138 is a numbered State Highway running in Rhode Island. It runs from the Connecticut state line to the Massachusetts state line and is the only state-numbered route that traverses the entire state.-Route description:...
  
   just west of the Jamestown-Verrazano Bridge
  Jamestown-Verrazano Bridge
  The Jamestown Verrazzano Bridge spans the West Passage of Narragansett Bay in Rhode Island, United States...
  
  . It heads north for another 3.3 miles (5.3 km) before crossing a branch of Wickford Harbor and turning right onto Brown Street, before turning left onto West Main Street and terminating, one half-mile west, at US-1.

History

At various points in time, every segment of Route 1A except the one in Westerly served as part of U.S. 1

U.S. Route 1 in Rhode Island

In the U.S. state of Rhode Island, U.S. Route 1 is a major north–south state highway through Providence. Staying close to the Atlantic Ocean and Narragansett Bay, it is a longer route than Interstate 95, and many portions are a four-lane divided highway....

 (historically the Lower Boston Post Road

Boston Post Road

The Boston Post Road was a system of mail-delivery routes between New York City and Boston, Massachusetts that evolved into the first major highways in the United States.The three major alignments were the Lower Post Road The Boston Post Road was a system of mail-delivery routes between New York...

). The Route 1A designation came after the U.S. 1

U.S. Route 1 in Rhode Island

In the U.S. state of Rhode Island, U.S. Route 1 is a major north–south state highway through Providence. Staying close to the Atlantic Ocean and Narragansett Bay, it is a longer route than Interstate 95, and many portions are a four-lane divided highway....

 designation was moved to a different alignment.

Before that, Route 1A existed on an alignment that is now roughly Route 3

Route 3 (Rhode Island)

Route 3 is a state highway in the U.S. state of Rhode Island.-Route:Route 3 takes the following route through the State:*Westerly: ; U.S...

.

The 19.0-mile (30.6 km) piece from old U.S. 1

U.S. Route 1 in Rhode Island

In the U.S. state of Rhode Island, U.S. Route 1 is a major north–south state highway through Providence. Staying close to the Atlantic Ocean and Narragansett Bay, it is a longer route than Interstate 95, and many portions are a four-lane divided highway....

 in downtown Wakefield to current US 1 near Wickford, now most of section 5 above, was once Route 1B. It was renumbered to Route 1A by 1934.