Finding a child to adopt and raise doesn't always happen within your state's borders, especially if you're adopting independently and working with an attorney or facilitator. A couple living in Ohio may be placed with a birth mother in Washington and while an adoption placement like this is spatially inconvenient, it's perfectly legal albeit a little more legally complicated than if a couple chose to adopt in their own state.
Since 1990, when New Jersey finally became the last state to adopt it, the Interstate Compact on the Placement of Children, or ICPC, has regulated the movement and placement of children over all state lines. Every state has a sending and receiving office that will monitor adoption parties, unless the child is being moved between relatives without state intervention. The ICPC office in the child's state of origin is called the sending office and will check-in with the receiving state and adoptive family post-placement. The sending state is the one with the right to remove the child if the ICPC office does not see the placement as a fit environment for a child. To avoid this, some states may require a criminal background check and screen for child abuse charges in addition to requesting a home study.
Out-of-state adoption can get tricky when it comes to statutory laws. Sending and receiving states may not always have complementary laws. This is why it's important to have a savvy adoption attorney.