Interior northern California

[RedSLC]

For context, I am referring to the area north of Sacramento that is not part of the coastal region.

For a very long time, this region was reliably democratic, it seems. For example, Shasta County (Redding) voted democratic in all but one election (1956) from 1932 to 1976. In 1972, some of the few counties McGovern won were in this area. In close elections, many of these counties went D.

However, it appears that since the 1980's, the area has become a republican stronghold. Both McCain and Romney won many of the counties in this region, even winning Redding, the largest city, with over 60 percent of the vote.

I am aware that the region's agricultural nature is what made it a democratic bastion in the past, but what exactly happened to cause such a massive turnaround?

[stevekamp]

Except for the Chico State vote in Butte County, the counterculture refigees in Nevada and Alpine, and the liberals around Lake Tahoe, Interior Northern California is an extension of the Rocky Mountain states without the urban areas.  These all started trending R in 1980, the year Republicans flipped the Redding US House district, which had been D since a 1943 special.

In 1976 Carter carried the 33 Interior counties but lost the coast.  In 2008 and 2012, the Obama margins in the 25 coastal (SoCal 7, Northern Pac Coast 18) were so big Obama could have received ZERO raw votes in the 33 Interior counties (including Yolo) and still won the state. 

[freepcrusher]

what exactly happened to cause such a massive turnaround?

those areas are pretty opposed to the environmentalists iirc.