In 1776, Congress ratified the Declaration of Independence. Four of its signers represented Maryland: Samuel Chase, William Paca, Thomas Stone and Charles Carroll. Try using this to remember their names: Paca Chased Carroll with a Stone. (Handout photo)

1802: The U.S. Military Academy opened at West Point, N.Y.

1863: Union troops under Gen. Ulysses Grant defeated Confederate forces at Vicksburg, Miss., ending a 14-month siege in the Civil War.

1997: NASA’s Pathfinder spacecraft landed on Mars, inaugurating a new era in the search for life on the Red Planet.

2004: A 20-ton slab of granite, inscribed to honor “the enduring spirit of freedom,” was laid at the World Trade Center site as the cornerstone of the future Freedom Tower skyscraper.

Compiled by Laura Lefavor and Paul McCardell.