Hi Victor,
OU has some great online courses (I teach in the MA in Museum Studies) - if you are not in OK but your state does not have a similar program I believe you qualify for in state rates -
https://online.ou.edu/programs/graduate/museum-studies/
https://online.ou.edu/programs/graduate/artsmanagement/
https://online.ou.edu/programs/graduate/artandtech/
I think the middle option has some Art History classes - I hope this helps!