Final answer:
The topic sentence is 'Alexander Hamilton’s major role in the US government was secretary of the Treasury,' which outlines the main focus of the paragraph about his contributions as the secretary.
Step-by-step explanation:
The topic sentence in the provided paragraph is "Alexander Hamilton’s major role in the US government was secretary of the Treasury." This sentence introduces the main idea of the paragraph, which details Hamilton's influence and actions as the secretary of the Treasury, including his strategies to strengthen the federal government's financial power and unify the nation economically.