The following states recognize same-sex marriage:

Notice a pattern? Most are located in the North. But if millennials show up to vote, things might change.

Millennials in general are more likely to support same-sex marriage over their parents with an overwhelming 70% in support. But southern millennials are not much different: nearly 65% support same-sex marriage, compared to only 28 percent of the Silent Generation (people born before 1942). 

The Atlantic attributes this shift in ideals to more young people having friends or family who have come out of the closet. However, sympathy doesn't always turn into equality, especially in a deeply religious part of the country. Millennials are becoming less religious and this could also explain the shift. 

One might think that more millennials supporting marriage equality would be effective in repealing the southern states' bans on same-sex marriages. But this has not translated to votes yet. For example, in 2012 North Carolina passed Amendment One that outlawed same-sex marriages. Broken down by county, the places that voted to lift the ban were largely college towns where a quarter of NC's population lives. But students were outvoted by the older, rural population who came out in droves to support the amendment. 

It's only a matter of time before popular support for marriage equality is fully realized. NC Republican House Speaker Thom Tillis even conceded it, calling called Amendment One "a generational issue,” that "would be repealed in 20 years." Hopefully it won't take as long as two decades for millennials to show up decisively...