Which river forms much of the border between Texas and Mexico?

Which city is known as "Steel City"? Which city is known as "The Twin Cities" together with Saint Paul? Which city is known as "The Magic City"? Which city is home to the Johns Hopkins Hospital and the Inner Harbor? Which river forms the border between Oklahoma and Texas for much of its length? Which river forms much of the border between Oregon and Washington? Which of the Great Lakes lies entirely within the United States? What is the name of the mountain range that runs through the eastern United States?