Why did the united states acquire new lands such as hawaii and alaska?

The land of Alaska was bought from Russia and the purchase was called Seward's folly as it was thought ridiculous. 

Hawaii was a sovereign nation with its own monarchy but populated by Americans, particularly the pineapple owners, who wanted to be a part of America to avoid various import taxes etc. They forced the then king to sign, at gunpoint, a new constitution which disenfranchised many voters and then used economic and political strength to eventually end the monarchy and make Hawaii a part of the US, both were voted in as states in 1959

The land of Alaska was bought from Russia and the purchase was called Seward's folly as it was thought ridiculous. 

Hawaii was a soverign nation with its own monarchy but populated by Americans, particularly the pineapply owners, who wanted to be a part of America to avoid various import taxes etc. They forced the then king to sign, at gunpoint, a new constitution which disenfranchised many voters and then used economic and political strength to eventually end teh monarchy and make Hawaii a part of the US, both were voted in as states in 1959