Benjamin Franklin was a man of vision. He was an inventor who created bifocals, a new kind of eyeglasses that people still wear to see better. Benjamin Franklin was also concerned about public welfare. He established the United States Postal Service and the first city hospital in America. In Philadelphia, he organized the police department, the fire department, the public library, and a university. He also helped write the Declaration of Independence and the Constitution. Today, millions of people benefit from the ideas that Benjamin Franklin had more than two hundred years ago. What is the main idea of this paragraph?

Most of the time, the main ideas of a paragraph are either placed at the beginning or at the end, and the author uses the rest of the paragraph to support the main idea. In this case, the main idea is placed at the end: Today, millions of people benefit from the ideas that Benjamin Franklin had more than two hundred years ago.

We can also infer that this is the main idea because the paragraph focuses on describing how Benjamin Franklin contributed to the progress of American society and society as a whole, and how those contributions still affect the lives of people nowadays: he invented bifocals (which are still used), he established Postal Service and the first city hospital in America, he organized several institutions in Philadelphia, and he helped write the Declaration of Independence and the Constitution (This latter being present nowadays).