split a field into different fields

[#1]

I have a field named 'sources'. For examples 1A_florida, 1B_florida, 1C_florida, 1A_georgia, 1B_georgia, 1C_georgia

If I want to create a new field '1A', '1B', '1C'. What is the best way to do this?

[#2]

I was thinking of displaying it in a different way but Miquel's solution is actually a better idea. Thanks everyone for their contribution.