The short answer is "We don't really know". Freemasonry wasn't simply founded one day, rather it grew out of a muddy and obscure guild system, probably some time in the 13th or 14th century. However, the organization that existed then was far from the modern day masonic lodges. In those days the members were really masons, the term Freemason is a reference to Freestone Mason, freestone being a kind of sand stone that is easily worked and used mostly for decorative purposes (in contrast of a rough mason who would work with harder stone).

The first grand lodges were formed in the early 18th century in London and with the election of Desaguliers as grand master the rise of speculative masonry (that is, members who are not actually stone masons) really caught on. It is from this point on that the organization starts to resemble modern freemasonry, it also marks the beginning of a rapid expansion.

I hope this answers your questions, if you have have questions about a specific lodge you can usually contact them directly for additional information.

Official dates we know:

• The Regius Poem - circa 1390, the first hint of "speculative" (philosophical) masonry.
• Lodge of Edinburgh No. 1, Edinburgh, Scotland - first verifiable minutes from 1599, and became a speculative Lodge circa 1600.
• Lodge Kilwinning, Scotland - records dating to 1642
• The founding of the Grand Lodge of England - 1717, this is the start of the modern governing structure of Freemasonry as a group of autonomous Grand Lodges that oversee national or sub-national jurisdictions.
• The founding of the Provincial Grand Lodges of Massachusetts and Pennsylvania - 1733 (Mass has the first recorded meeting of the Provincial Grand Lodge)
• The split in the Fraternity during the 18th century ended in 1813.