1. Hiram Bingham III: Told the world about Machu Picchu

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Bingham is credited with becoming the first outsider, in 1911, to visit the ruins of Machu Picchu, the now-famous Inca settlement in the Peruvian Andes that was built in the 15th century and abandoned around the time of the Spanish conquest of the Inca Empire in the 16th century. Born in 1875 to Christian missionaries in Hawaii, Bingham earned a Ph.D. from Harvard and married a Tiffany & Co. heiress, whose wealth helped fund his expeditions. In 1911, Bingham, then a Yale University faculty member specializing in South American history, was in Peru searching for Vilcabamba, the last Inca outpost before it fell to the Spanish when he encountered a local farmer who directed him to the ruins of Machu Picchu.

Although the site was known to peasants living in the region, its existence had never been publicized. Bingham, who returned to Machu Picchu (meaning “old peak” in Quechua, one of Peru’s native languages) in 1912 to conduct a major excavation and made a third visit to the area in 1914-15, documented his sensational findings in a series of articles and books. Although some experts later contended that missionaries and other non-locals might have visited Machu Picchu before Bingham, he was the first to conduct a scientific exploration of the site.

In addition to his days as an explorer, Bingham commanded a flight school in France for the American military during World War I and then went on to represent Connecticut in the U.S. Senate from 1925 to 1933. He died in 1956. In 2010, after a lengthy custody dispute, Yale University reached an agreement with the Peruvian government to return thousands of artifacts Bingham had excavated from Machu Picchu.

2. Mary Kingsley: Traveled solo through Africa in Victorian garb

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During the Victorian era, a time when British women were expected to carry out their lives in the domestic sphere, Kingsley defied society’s expectations and traveled extensively on her own throughout West Africa, where she studied the customs of local tribes and was the first European to visit certain remote areas.

Born into a middle-class English family in 1862, Kingsley had no formal education and spent many years caring for her invalid mother. It was only after her parents died, within a short period of each other in 1892, that the unmarried Kingsley was able to escape her domestic duties and leave home. Starting in 1893, she made two extended trips to West Africa, where she got around by canoe and by foot (all while decked out typical female Victorian garb: high-necked blouses and long skirts); came in contact with cannibals and dangerous wildlife; collected fish specimens for the British Museum (three types of fish later were named for her); and scaled 13,000-foot-high Mount Cameroon.

She went on to pen two influential books, including “Travels in West Africa” (1897) and became a celebrity in England, where she spoke out against British colonial policies in Africa. Kingsley contracted typhoid while serving as a nurse to Boer War prisoners and died in South Africa in 1900.

3. Thor Heyerdahl: Sailed the high seas in primitive crafts

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In the second half of the 20th century, Heyerdahl explored the world’s oceans on vessels made of reeds and papyrus in an effort to promote his theories about the migration patterns of ancient peoples. Born in Norway in 1914, Heyerdahl studied biology and geography at the University of Oslo then in the late 1930s spent a year on an isolated Polynesian island, conducting research and living off the land. During this time, he began formulating his theory about how the first human settlers had reached the South Pacific islands. Heyerdahl came to reject the prevailing belief that the islands had been settled by people from Southeast Asia who had sailed against the ocean currents for thousands of miles; instead, he postulated that these prehistoric migrants had traveled west from South America.

In 1947, in order to test his theories, Heyerdahl, along with five other men, made a 101-day, 4,300-mile voyage across the Pacific Ocean, from Peru to the Polynesian islands, aboard a 40-square-foot raft, the Kon-Tiki. The craft was constructed of balsa wood and reeds using only the basic tools that would’ve been available to ancient South Americans. Despite the Kon-Tiki’s successful voyage, most scholars discounted Heyerdahl’s migration theories. Nevertheless, a book Heyerdahl wrote about his journey became a best-seller and was translated into dozens of languages, while a documentary he produced about the Kon-Tiki won an Oscar in 1951.

Heyerdahl’s subsequent scientific projects included archaeological expeditions to the Galapagos Islands and Easter Island in the 1950s; a voyage across the Atlantic Ocean in a papyrus boat, the Ra II, in 1970; and a voyage across the Indian Ocean in a reed boat, the Tigris, in 1978. He continued to explore the world and pursue various scientific endeavors until his death from cancer in 2002.

4. Gertrude Bell: Made her mark on the Middle East

A British adventurer, diplomat and archaeologist, Bell traveled widely throughout the Middle East and played a leading role in the creation of the modern Iraqi state in the early 1920s. Born into a wealthy English family in 1868, Bell studied history at Oxford University and then spent a number of years trekking around the world, mastering multiple languages (including Arabic and Persian) and pursuing her interests in archaeology and mountaineering. She published various accounts of her expeditions, including a 1907 book titled “The Desert and the Sown,” about her journey across Syria.

At the start of World War I, Bell, along with T.E. Lawrence (aka Lawrence of Arabia) became part of a British military-intelligence gathering operation in Cairo known as the Arab Bureau. Bell went on to work as a diplomat in Baghdad during and after the war and was instrumental in defining the borders of the modern state of Iraq and installing Faisal I as its new king, in 1921. Additionally, Bell helped found the Baghdad Archeological Museum (now called the National Museum of Iraq) before she died of an overdose of sleeping pills in 1926. Paradoxically, even though Bell was a powerful woman in a male-dominated world, she didn’t believe that women were smart enough or experienced enough to vote and campaigned against female suffrage.

5. William Beebe: Explored the ocean at new depths

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Before there was Jacques Cousteau, there was Beebe, an explorer and naturalist who in the early 1930s pioneered the use of an underwater craft called the bathysphere to explore the ocean at depths no human had ever gone before. Born in Brooklyn, New York, in 1877, Beebe attended Columbia University and then took a job as a curator of birds at the New York Zoological Park (now the Bronx Zoo), which opened in 1899. He went on to travel the world conducting field research and collecting specimens for the zoo. Beebe, whose friends included fellow naturalist Theodore Roosevelt, developed an interest in oceanography and in the late 1920s met Otis Barton (1899-1992), inventor of the bathysphere.

Beebe and Barton first tested the 5,000-pound, 4.5-foot-wide, ball-shaped steel vessel (which was suspended from a mother ship by a cable) off the coast of Bermuda in 1930. Four years later, the two made a record-breaking dive of 3,028 feet (more than half a mile down) in the bathysphere, whose name was derived from the Greek word “bathys,” meaning “deep.” From the craft’s portholes, Beebe cataloged never-before-seen marine life. The bathysphere’s deep-sea dives received national media coverage, and Beebe himself captivated audiences across America with his radio broadcasts from the vessel. He died in 1962.