While no one knows when Solitaire was invented, it is generally accepted that some version of the game was developed as soon as playing card games became popular around the time of the Middle Ages.
The most widely accepted idea is that the French were responsible for developing the more popular versions of Solitaire. Some historians even go so far as to say that Napoleon Bonaparte invented the game while in exile in on the island of St. Helena. Many forms of Solitaire of that time period relate to Napoleon. Other historians claim that Solitaire originated from Eastern Europe, based on early books found on the subject.