Most socially conservative county with a population of over 500,000?

[RedSLC]

Utah County, Utah, hands down. It's home to the biggest socon legislators in the state (like State Senator John Valentine, an extreme anti-alcohol zealot behind Utah's infamous "Zion curtain" laws), and consistently gives strong support to socon causes. Amendment 3, which banned gay marriage and civil unions back in 2004 had the strongest support here of any county in the state, with 82% voting in favor. Not even the rural counties could match Utah.

The closest runner-up would be Montgomery County, Texas, but it's neither as heavily populated or as conservative as Utah County (although, it certainly is very right-wing, don't get me wrong). For counties that meet the actual 500k threshold, I'd order them, starting with the most socially conservative:

1. Utah County, UT
2. Oklahoma County, OK
3. Kern County, CA
4. Collin County, TX
5. Tulsa County, OK
6. El Paso County, CO
 

[RedSLC]

Utah County, UT; Tulsa County, OK; and El Paso County, CO are definitely in the running.

No Kern County, CA? It was Proposition 8's strongest county (it passed by a 3-to-1 margin there), and also voted heavily in favor of restricting abortion and heavily against legalizing marijuana.

[RedSLC]

Salt Lake County   Utah Salt Lake has some non-Mormons.

I should know fixed the spelling, BTW.

As for the others:

Kern County   California

Tarrant County   Texas Too much of downtown Fort Worth in here.
Collin County   Texas
Hidalgo County   Texas
Denton County   Texas Home to North Texas University, which will bring it down somewhat.

Utah County   Utah

Duval County   Florida
Lee County   Florida
Polk County   Florida     I'd say Polk is the most socon of the three.

Oklahoma County   Oklahoma
Tulsa County   Oklahoma

El Paso County   Colorado

Kent County   Michigan Too much of a swing county to be among the most socially conservative.

Lancaster County Pennsylvania

Sedgwick County   Kansas