State Route 100 is a 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 the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Maine

Maine

Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...

, running from Portland to Bangor.

The south end of State Route 100 is at the intersection of Forest Avenue and Park Avenue in downtown Portland, the same place U.S. Route 302 ends. Both US 302 and State Route 100 pass under U.S. Route 1 and Interstate 295

Interstate 295 (Maine)

Interstate 295 is a -long connector in the U.S. state of Maine from I-95 in Scarborough to I-95 in West Gardiner.-Route description:...

 at the Forest Ave. cloverleaf

Cloverleaf interchange

A cloverleaf interchange is a two-level interchange in which left turns, reverse direction in left-driving regions, are handled by ramp roads...

 (Exits 6A-B), not far from the Park Avenue intersection.

State Route 100's north end is at the intersection of Hammond Street, Main Street, State Street and Central Street in downtown Bangor; State Route 100 runs along Hammond Street with U.S. Route 2

U.S. Route 2 (Maine)

In the U.S. state of Maine, U.S. Route 2 is a principal east–west route through the central portion of the state.-Route description:After crossing the New Hampshire state line in Gilead, Route 2 continues to follow the Androscoggin River, turning north in Bethel...

 (which continues across Main Street/Central Street onto State Street). This is also the east end of U.S. Route 202, which runs along Main Street. (State Street is one-way eastbound, so traffic on US 2 west uses Central Street.)

Concurrent routes

The majority of State Route 100 is concurrent with other routes:

• U.S. Route 302, downtown Portland to northern Portland
• State Route 26, northern Portland to Gray
• U.S. Route 202, Gray to Augusta
• U.S. Route 201, Augusta to Fairfield
• State Route 11
  State Route 11 (Maine)
  State Route 11 is a state highway in Maine. It connects to New Hampshire Route 11 at its south end in Lebanon and travels through the counties of York, Cumberland, Androscoggin, Kennebec, Somerset, Waldo, Penobscot, Piscataquis, and Aroostook. The road ends at U.S...
  
  , Fairfield to Newport
• U.S. Route 2
  U.S. Route 2 (Maine)
  In the U.S. state of Maine, U.S. Route 2 is a principal east–west route through the central portion of the state.-Route description:After crossing the New Hampshire state line in Gilead, Route 2 continues to follow the Androscoggin River, turning north in Bethel...
  
  , Newport to downtown Bangor

The only part of State Route 100 that does not run along another route is between US 302 and State Route 26 in northern Portland, where it is alone on a piece of Allen Avenue.

Alternate route

State Route 100A is a 5.2 miles (8.4 km) alternate of Maine State Route 100 running between the towns of Winslow

Winslow, Maine

Winslow is a town and census-designated place in Kennebec County, Maine, United States, along the Kennebec River. The population was 7,743 at the 2000 census.-History:...

 and Benton

Benton, Maine

Benton is a town in Kennebec County, Maine, United States. The population was 2,557 at the 2000 census. The town was named for Missouri Senator Thomas Hart Benton.-Geography:...

.

Route 100A's alignment was formerly part of Maine State Route 32, before Route 32 was truncated in 1954 to end at Route 137 Business, near its intersection with US-201/Route 100 just south of Route 100A's current terminus. The old alignment , which connected to Route 100 at both ends, was redesignated as Route 100A (as a bypass of Route 100's alignment in Winslow and Benton). As such, Route 100A is a former alignment of Route 32, and not of its parent, Route 100.