The free fishing days for 2019 have been announced for each state. On these specific days, unique to each state, you are allowed to fish without a fishing license. Most of the 2019 dates seem to fall around early June, but there are plenty of May, July, and August dates on there as well.
On a related note, I learned about the existence of fishing licenses the hard way. I was grateful the game warden took pity on me when he saw I not only failed catching a single fish, but was also tangled in the fishing line when he pulled up.
Saved by my own ineptitude!