husband in prison in another state

A person is unlikely to be considered a resident of a state if that person’s only connection to the state is being incarcerated there. 

• Most states have specific residence laws for incarcerated people. Generally, incarcerated people retain their home addresses as their official residence even when they are incarcerated across the states. 
• Contact your Department of Revenue to review the residency requirements in your state.

Note: If the inmate performs services for any payor, even a private company, while in jail, the wages received are not earned income for the CTC or EITC. Additionally, the status of where the inmate performs the work is irrelevant for the above rule. Ineligible income also includes amounts paid for work performed while in a work release program or while living in a halfway house.

He lived in Illinois before his incarceration and has never lived in my state. Can I do state taxes for me only? I live in Louisiana?

Yes:  if you file jointly on your federal return, Louisiana law requires that you file jointly on your state return, as well.

See Lines 1-5 – Filing status in the Instructions for Preparing Your 2020 Louisiana Resident Income Tax Return Form (IT-540).