A question about lumber...?

I would like to buy lumber, ideally 1/4"x4"x6', but I can go as thick as 1/2"x4"x6'. Width has to be 4" exact, length has to be minimum 6'. The only cut I can find at my local home improvement store is 1"x4"x6'. Can the store (Lowe's/Home Depot) cut the 1" lumber down to 1/2" or even 1/4" thickness? I am buying poplar, if it makes any difference.