What's the common trait?

I should've called this thread "State Math Problem II".



What trait do these counties have in common:

Cherry County, Nebraska

Elko County, Nevada

Gulf County, Florida

Idaho County, Idaho

Malheur County, Oregon



Go ahead & use the internet if you want. I don't care. It's not like I'm giving away prizes. I'll even put the answer here:

Spoiler:

Seriously, the next spoiler is going to have the answer, and, it's somewhat underwhelming, so I hope you're not expecting much:

Spoiler:

Each county has two different time zones.

Now you add a list.

What's the common trait?