Their oil!
What made Alaska valuable to the United States was all the gold and silver, base metals like lead and zinc, timber and seafood.
The Hawaiian Territory was more valuable than the Alaskan Territory.
Alaska
They had oil available for great profit.
Oil and natural gas.
Yes.
Having a war
The Gold Rush of 1849
This would be Alaska. Russia sold Alaska to the US, believing it was worthless. However the US later found gold and oil in Alaska.
Alaska's most valuable mineral product is gold, according to the State of Alaska. Following gold, the next most valuable product is zinc. Fuel products are the state's biggest money makers, but geologists do not consider coal or petroleum to be minerals.
Natural diamonds are more valuable than manufactured diamonds, most of which are made for industrial applications, not for use as gemstones.
more valuable