The branch of government that was involved in the annexation was Congress or the Legislative.
What is the role of Congress?
Congress has several roles and one of them is to approve treaties that the United States signs with other nations and international organizations.
Annexations of territory to the U.S. such as Alaska, required a treaty with another nation which meant that Congress would have to be the branch of government involved.
Find out more on the roles of Congress at https://brainly.com/question/24173581.
