21 year old from WI, lived in NC for college and MN for summer job. Visited parents in in WI. What is state of residency? File returns in all 3 states or just the 2?

I never changed residency from WI but I never truly resided there.  I would visit for a few days during breaks from school and work.  Do I need to file in WI even though I never worked in WI.  I have W2s from NC and MN from my work in those states.