J.B.
Sorry but there are very few circumstances where I think it's OK for a custodial parent to move out of state. If your ex provided no support, didn't use his visitation, and you lived in an area where you couldn't support yourself and your child due to circumstances outside of your control (an industry drying up or moving out of the region, disability, needing to care for an aging parent, etc.) and the move put you closer to family or you had a job there that you couldn't get where you live, then it's reasonable. Outside of scenarios like that? Not so much. This seems more like a wish than a necessity the way you phrased it.
Why do you want to move? I think that you will need to be prepared to argue that to your ex and, if contests, to a judge. And you need to be prepared to have him fight you for custody over it. My son has a friend whose mom tried to move out of state...his dad fought for custody and won, so now the boy lives here with his dad, step-mom and half sibling during the school year and he spends summers visiting his mother out of state.
I hope you can find a solution that works for all of you but be very careful moving forward and before you start down this road, make sure that it really is your only option. Because to take a child away from a loving, involved parent for long periods of time for any reason other than pressing need would be selfish and cruel to the child (and the other parent).