Its borough seat is Palmer, and the largest community is the census-designated place of Knik-Fairview.

The Mat-Su Borough is so designated because it contains the entire Matanuska and Susitna Rivers.

They empty into Cook Inlet, which is the southern border of the Mat-Su Borough.

The borough seat is Palmer,[4] and the largest community is the census-designated place of Knik-Fairview, Alaska.

[13] Though the borough has aligned with the statewide presidential election winner in Alaska in every election since statehood, it has come to stand out as one of the most Republican areas in Alaska, alongside the neighboring, less populated Southeast Fairbanks Census Area.

[14] Sarah Palin was previously the mayor of Wasilla, the largest city in the borough.

[15] The borough declared a state of emergency[16] and incurred over $2 million in costs.