Twain in the laboratory of Nikola Tesla, early 1894 — Originally published as part of an article by T.C. Martin called "Tesla's Oscillator and Other Inventions" that appeared in the Century Magazine (April 1895),
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=7231469

Birthplace of Mark Twain in Florida, MO —
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=2872819

Twain House in Hartford, CT —
Photo Credit: By Cliff - Flickr: Mark Twain House and Museum, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=16488910

Olivia Langdon — At about 24 years-old
Photo Credit: By unattributed - Public Domain, https://commons.wikimedia.org/w/index.php?curid=11359930

Twain in 1907 —
Photo Credit: By A.F. Bradley, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11351079

Windmill scene from Don Quixote — by Gustave Dore, 1863
Photo Credit: Miguel de Cervantes's Don Quijote. Illustrations by Gustave Dore., Public Domain, https://commons.wikimedia.org/w/index.php?curid=47159175

Cropped Flag of Bosnia and Herzegovina —
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=342986

Petar Lubarda's Kosovski Boj —
Photo Credit: By Orjen - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=40776285

Coat of arms of Genoa —
Photo Credit: By Facquis - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=88171271

Schlacht von Nikopolis —
Photo Credit: By aus Sébastien Mamerot - Sébastien Mamerot, Les Passages d’Outremer, Public Domain, https://commons.wikimedia.org/w/index.php?curid=16193258

Cropped Flag of Serbia —
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=65419036