1. The 1876 Century Safe

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The Century Safe, c. 1876.

The world’s first planned time capsule debuted in 1876 when New York magazine publisher Anna Deihm assembled a “Century Safe” at the U.S. Centennial Exposition in Philadelphia. The iron box was stuffed with 19th-century relics including a gold pen and inkstand, a book on temperance, a collection of Americans’ signatures, and snapshots of President Ulysses S. Grant and other politicians taken by photographer Mathew Brady. After being sealed in 1879, the purple velvet-lined safe was taken to the U.S. Capitol and eventually left to languish under the East Portico. Though nearly forgotten, it was later rediscovered, restored and unlocked on schedule in July 1976 during the nation’s bicentennial festivities. At a ceremony attended by President Gerald Ford, Senator Mike Mansfield said the opening had honored “the wish of a lady who sought to speak to us from the other side of a 100-year gulf.”

2. The Massachusetts State House Time Capsule

The United States’ oldest known time capsule was the work of none other than Samuel Adams and Paul Revere. In late 2014, repairmen fixing a water leak at the Massachusetts State House uncovered a brass box that the two former Sons of Liberty had placed in a cornerstone to mark the building’s construction back in 1795. It had already been opened once in 1855 for cleaning and the addition of new artifacts, and historians were initially unsure if its contents had survived intact. When it was finally unsealed in 2015, however, it was found to contain a trove of preserved artifacts including newspapers, coins dating back to the 1600s, a page from the Massachusetts Colony Records and a copper medal with an image of “General of the American Army” George Washington. Most exciting of all was a silver plaque—most likely the work of Revere—that read, “This cornerstone of a building intended for the use of the legislative and executive branches of the government of the Commonwealth of Massachusetts was laid by his Excellency Samuel Adams, Esquire, governor of the said Commonwealth.”

3. The Crypt of Civilization

Most time capsules contain only a few trinkets or letters, but Oglethorpe University’s “Crypt of Civilization” represents an audacious attempt to preserve all of human knowledge for posterity. The project was the brainchild of the university’s president, Thornwell Jacobs, who believed it might serve as a valuable record for archaeologists in the distant future. Beginning in 1937, he converted an underground 20-by-10 chamber in the administration building into a museum of civilization filled with everything from 640,000 pages of microfilmed books and religious texts to an early television, a container of beer and a set of toy Lincoln Logs. The vault even features a special “language integrator” to help teach English to whoever might find it. The entire haul was welded off behind an airtight stainless steel door during a ceremony in May 1940. Jacobs decreed that it should remain closed for 6,177 years—the same amount of time that was then thought to have passed since the beginning of recorded history. The Crypt remains at Oglethorpe University to this day, and is now more than 75 years into its long journey to the year 8113 A.D.

4. The Westinghouse Time Capsules

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Monument to the Westinghouse time capsules.

During the future-themed 1939 New York World’s Fair, the Westinghouse Electric and Manufacturing Company entombed a torpedo-shaped cylinder inside a 50-foot-deep “Immortal Well” on the fairgrounds in Flushing Meadows. The cylinder was originally called a “time bomb,” but the name was changed after a Westinghouse publicist coined the now-famous term “time capsule.” Another capsule was placed nearby in 1965, and both are now scheduled for opening in the year 6939 A.D.— 5,000 years after the first one was buried. The items inside the two capsules include a collection of seeds, metals and textiles; microfilm and newsreels; and everyday items such as a Beatles record, a bikini, a pack of Camel cigarettes and a plastic child’s cup featuring Mickey Mouse. The 1939 capsule also featured a letter from physicist Albert Einstein, who praised the scientific progress of his age but also added that “People living in different countries kill each other at irregular time intervals, so that also, for this reason, anyone who thinks about the future must live in fear and terror.”

5. The Detroit Century Box

Shortly after the clocks struck midnight on January 1, 1901, Mayor William C. Maybury sealed a copper time capsule at Detroit’s Old City Hall and proclaimed that it was not to be touched for 100 years. When Detroit Mayor Dennis Archer finally opened the “Century Box” in December 2000, it was found to contain several dozen letters to the future written by the city’s business and political leaders. Most of the missives included descriptions of the wonders of 1900 Detroit along with musings on what life in 21st century might be like. “How much faster are you traveling?” Maybury asked his future successor. “We talk by long distance telephone to the remotest cities in our own country…Are you talking with foreign lands and to the islands of the sea by the same method?” Other prognosticators were not so accurate. A few speculated that Canada would be annexed or that Ontario would become a U.S. state, and the Metropolitan Police Commissioners wrote that, “prisoners instead of being conveyed to the several police stations in Automobile patrol wagons will be sent through pneumatic tubes, flying machines, or some similar process.”

6. The Expo ’70 Time Capsule

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Expo 70 Capsule site in Osaka.

1939 wasn’t the only year that a world’s fair included an ambitious time capsule project. For the 1970 Expo in Osaka, Japan, the electronics giant Panasonic constructed a kettle-shaped capsule designed to remain unopened for 5,000 years. The main container was filled with a protective layer of inert argon gas to protect its contents, but the project leaders also built a second “control” capsule that will be periodically opened, inspected and cleaned to ensure its survival and help keep the project’s memory alive. The first opening already took place in 2000, and the rest will occur at intervals of 100 years. In total, each capsule contains a cargo of 2,098 culturally significant objects, many of them suggested by the public. If the two capsules endure until the planned opening date of 6970 A.D., their future owners will find an extensive collection of films, seeds and microorganisms as well as a ceremonial kimono, a Slinky and even the blackened fingernail of a survivor of the 1945 Hiroshima atomic bombing.

7. The Juneau Time Capsule

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Juneau, Alaska’s Federal Building includes an unusual attraction in the form a room-sized time capsule fitted with a plate glass observation window. First closed off in 1994, the 9-by-6-foot chamber is packed with thousands of pieces of memorabilia scrounged by locals as part of a citywide project. Many of the objects are everyday relics of the 90s—a Wonderbra, a Sony Walkman, a Barbie doll—but there are also old driver's licenses, family mementos and a box containing menus from all of Juneau’s restaurants. The vault also includes hundreds of letters written by schoolchildren to the students of the future. Copies of the notes were put on display several years later, but the originals will remain sealed off until New Year's Eve 2094—the date when the capsule is scheduled to be opened after 100 years. “If you want to include me in your history book as the best fifth grader in the year 1994-1995,” one student wrote, “go ahead and do it.”

8. The Future Library

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Scottish artist Katie Paterson’s Future Library is a literary time capsule that will be a century in the making. Starting in 2014, a new author will be invited to submit a novel, poem or other written text to the project each year for 100 years. In 2114, the entire collection will be published all at once—no doubt posthumously for many of its contributors. A forest of 1,000 trees has already been planted outside Oslo, Norway to supply the paper for the printing. None of the entries will be available to read until the project is complete, however, and the writers are forbidden to reveal anything about their works other than the title. Canadian novelist Margaret Atwood submitted the first manuscript, called “Scribbler Moon,” in 2014, and British author David Mitchell provided the second the following year. Their manuscripts, along with 98 forthcoming titles from other writers, will be held in a public library in Oslo until their official unveiling in the 22nd century.