This is a list of notable events in the history of graffiti.  Sources that I consulted during the writing of each synopsis are given at its end.  Each milestone is a stop along the way towards the current state of modern graffiti.

Mexican-American pachucos began creating street art using spraypaint.  This movement was occurring in East Los Angeles in the 1930s.  The style underwent an evolution of style from Old English to prison style and was used to create roll calls of gang members and deliniating neighborhoods.  Current propagators of the Cholo style are artist Chaz Bojorquez and tattoo artist Mr. Cartoon (Mark Machado).  The use of Old English lettering is noteworthy because within Mexican-American culture this lettering style is afforded a measure of authority and credibility.

From late 1939 into the early 1950s the phrase "Kilroy was here" and also an accompanying big-nosed peek-a-boo faced drawing sprung up all over the globe.  There are many stories about the origin of the phrase and drawing.  The more credible accounts attribute their spread to American G.I.'s during World War II.  The phrase "Kilroy was here" was attributed to James J. Kilroy in a 1946 New York Times report.  James J. Kilroy was a welding inspector for the Bethlehem Steel Shipyard in Quincy, Mass.  Inspectors marked the pieces after they were inspected to prevent multiple inspections.  Shorter marks could be erased and then the piece inspected by a second employee who would receive the credit (and the pay).  A longer mark would insure proper credit for work accomplished.  As imitation is the highest form of compliment, Kilroy's phrase was imitated by other shipyard workers who were subsequently drafted.  These servicemen spread the phrase "Kilroy was here" all around the globe.

Aerosol cans were patented on November 23, 1927 by a Norwegian named Erik Rotheim.  The use of the aerosol can for the conveyance of paint was implemented by Edward Seymour in 1949.  He founded Seymour of Sycamore, Inc. in Chicago, IL, and the manufacture of spray paint began.

Demitrius lived in Manhattan and during 1971 became famous as Taki 183.  The young Greek-American became the subject of a New York Times article titled "Taki 183 Spawns Pen Pals" and this glimpse of the notoriety afforded to a name exploded into the tagging phenomenon.  To be sure, there were other taggers.  One often cited writer is "Julio 204" who was up around NYC in the 1960s.