1861: Joins volunteer militia called the Marion Rangers, which drills for two weeks and then disbands. Clemens travels west to Nevada territory with brother Orion, where they mine for silver. That summer, President Lincoln names Orion secretary of the territory. Clemens works as his brother's secretary.

1862: Clemens begins working as reporter for the Virginia City Territorial Enterprise, the Nevada Territory's best-known newspaper.

1863: Leaves Nevada to avoid prosecution on anti-dueling laws after challenging a rival editor to fight. Adopts the pen name Mark Twain -- a river call that tells a captain the water ahead is safe to navigate. A call of "mark twain" indicates the water is two fathoms, or 12 feet, deep.

1864: Moves to San Francisco, goes to work as reporter for a local paper, writing for the Golden Era and other publications. Becomes important figure in the San Francisco literary scene.

1866: Takes a four-month trip to Hawaii as correspondent for The Sacramento Union. His "Sandwich Islands Letters" are so popular that he begins a lecture tour throughout California and Nevada. He leaves California at the end of 1866, moves to New York City and continues to lecture. The lecture tour secures his reputation as a popular and established speaker.

1867: Clemens' first major work, "The Celebrated Jumping Frog of Calaveras County, And Other Sketches," is published. He leaves New York in June to travel to Europe and the Middle East. The trip inspires his travel book, "The Innocents Abroad." Moves to Washington, D.C., becomes the private secretary to Senator William Stewart of Nevada.

1868: Becomes engaged to Olivia (Livy) Langdon.

Photos courtesy of Mark Twain Collection (#6314), Clifton Waller Barrett Library, The Albert H. Small Special Collections Library, University of Virginia Library.