Encyclopædia Britannica is the oldest English-language general encyclopedia still in print. The first edition of the Encyclopædia Britannica was a three-volume set published one section at a time over a three-year period, beginning in 1768. The company developed Britannica Online, the first encyclopedia for the Internet in 1994. 
Encyclopædia Britannica 1911
The 11th edition of the Encyclopædia Britannica was published in 1910 - 1911. As it is entirely in the public domain, articles of this 29-volume work were used to start corresponding entries on various web-based encyclopedias, e.g., Wikipedia. It is widely considered to be the finest Britannica, if not one of the finest encyclopedias ever created.
http://www.britannica.com/ Official website