Alexis,
It wasn't that Sweden claimed the state, Delaware wasn't a state in 1631 and the Swedes claimed only the Delaware river valley because of Henry Hudson's explorations in the first decade of the 17th century.
Gehring, Charles T. (1995), "Hodie Mihi, Cras Tibi", New Sweden in America Swedish-Dutch relations in the Delaware Valley (University of Delaware Press), ISBN 0-87413-520-6.
Hope this helps!
Neal