JUNEAU (AP) — A fast-growing area north of Anchorage known as a hotbed of conservatism gained the most population since the 2010 Census but will keep the same number of House seats in the Legislature under a new map of state political boundaries that some critics say shortchanges the area.

Census data showed the Matanuska-Susitna Borough, which is about the size of West Virginia and includes Palmer and former Gov. Sarah Palin’s hometown of Wasilla, had 18,086 more people last year than in 2010, the biggest jump for any borough or Census area in Alaska.

The region also was the second mos...