Early 1800s: In 1803, after the Louisiana Purchase, the area of the United States is 1,716,003 square miles, stretching across the North American continent to the Rocky Mountains.

Today: The area of the United States is 3,717,796 square miles including Alaska and Hawaii.

Early 1800s: In 1805, the U.S. population is about 6.3 million, up 1 million from five years earlier. The western regions see enormous growth; for instance, the population of Louisiana grows from 77,000 in 1810 to 153,000 in 1820.

Today: The U.S. population is over 270 million.

Early 1800s: In 1803, war breaks out between longtime enemies France and Great Britain.

Today: Both France and Great Britain are members of the European Union (EU), an organization with the goal of creating economic and political ties among the countries of Europe. In 1999, the EU introduces the "euro" as its common currency.

Early 1800s: In 1803, vast quantities of the North American continent are...