Most residents of Alstahaug live in the town of Sandnessjøen which is situated on the island of Alsta.

The island is connected to the mainland via the large Helgeland Bridge along Norwegian County Road 17.

[5][6] The large prestegjeld of Alstahaug was established as a municipality on 1 January 1838 (see formannskapsdistrikt law).

Just two years later, in 1864, the western island district (population: 2,438) was separated to become the new Herøy Municipality.

The linguist Magnus Olsen believed this old island name means "eel grounds" and it was an old taboo word for the sea.

The official blazon is "Argent, a fess engrailed azure" (Norwegian: I sølv en blå bjelke dannet ved taggesnitt).

The design symbolizes the Seven Sisters (Norwegian: De syv søstre), a row of mountains in the area, mirrored in the clear waters of the fjord.

Lying just south of the Arctic Circle in an area that is known as Outer Helgeland, Alstahaug offers the visiting bird watcher a chance to do some birding in spectacular scenery, be it coastal or inland where The Seven Sisters mountain chain marks the boundary between the habitats.

[1] The official weather station is located at Sandnessjøen Airport, Stokka, on Alsta island.

The municipal council (Kommunestyre) of Alstahaug is made up of 27 representatives that are elected to four year terms.

The tables below show the current and historical composition of the council by political party.