ABA

The ABA website has a search engine where you can come by some interesting and helpful info.

Here is a question I stumbled upon:

How many states allow divorcing parents to have joint legal custody of their children? How many states have a presumption in favor of joint legal custody?

All states permit parents to have joint legal custody of their children after a divorce. As of 1996, 43 states and the District of Columbia have statutes that specifically authorize the courts to order joint custody. (In some states, joint custody is referred to as shared custody.) In the 43 states with joint legal custody statutes, 11 states and the District of Columbia declare a presumption in favor of joint custody, which means that courts are supposed to grant joint custody unless there is proof that joint custody is not in the child's best interest. In addition, eight states declare a presumption in favor of joint custody if both parents agree to it. The remaining 24 states with joint custody statutes make joint custody an explicit option without any presumption for or against joint custody. Seven states do not have joint custody statutes, but courts in those states can use their equitable powers to order joint custody in appropriate circumstances. Joint custody usually is considered appropriate when the parents appear willing to cooperate in raising their children.

And this links to a chart by state