Carbon dating of materials from Machu Picchu date the ruins to the fifteenth century. Archeologists think that the fortress of Machu Picchu was built during the period between 1438 and 1471. Most archeologists agree with the idea that Machu Picchu was built as a part of sacred grounds as a place to worship the Incan gods. In addition, the inaccessible location of Machu Picchu made it easy to defend from any potential attackers.

Why the fortress was abandoned remains a mystery today. Theories as to why it was forgotten to history include the idea that because only the upper echelon were aware of its location, once they died out, no one was left to remember its existence.

The ruins were returned to Peruvian and international memory upon its discovery by Hiram Bingham, a Yale anthropologist, and a team of fellow scientists in 1911. An earlier group of men had rediscovered it in 1901, having left their names on the ruins; however their discovery was not widely discussed, thus giving first credit to Bingham and his team.

The site was declared an historical sanctuary on January 8, 1981 and added to the World Heritage List in 1983.

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