| The original mason jar, invented in 1858, consisted of a glass jar with a screw-threaded neck and a zinc jar-cap, capable of screwing onto the jar's top tight enough to create an air-tight seal where the lip of the cap met the shoulder of the jar, creating what is known as a shoulder-seal.
In 1869 the mason jar with which we are all now familiar was invented when the cap was divided into a metal ring, containing the threads, a metal plate that fit snugly underneath the threaded ring, and a rubber ring that fit between the lip of the bottle and the metal plate. When the top assembly was screwed down tightly, the compression of the rubber pushed the metal plate above it into the screwed on ring, creating an exceedingly airtight seal.
One might be tempted to assume that the name mason jar is of masonic origin due to the fact that the mason jar's chief strength is its hermetic seal and that the origin of the mason jar corresponds closely to a time when masonic and hermetic societies were enjoying a fair degree of intercommunication and even fusion (e.g. the hermetic order of the golden dawn). The truth is far less conspiratorially savvy: The Mason jar is named after its inventor, John Landis Mason of Pennsylvania.
The mason jar was an incredible innovation in an age when people still performed a lot of their own food preservation -- especially in massively agrarian societies such as The United States. Previous methods of preserving foods involved cumbersome apparati in order to create air-tight seals. The mason jar, by contrast, was easy to use and perhaps more importantly easy to reuse: only the metal plate was usually replaced before a mason jar could be used to hold some other preserved vegetable matter.
Sources:
McClung Museum, "Object of the Month - Mason Jar",
http://mcclungmuseum.utk.edu/objectmo/ob-9808.htm
Aboriginal Innovations in Arts, Science and Technology Handbook, "Screw-top Jar",
http://www.schoolnet.ca/aboriginal/handbook/technology_screw-top-jar.html | 
