Arsenal were formed as Dial Square in 1886 and the first crest the club adopted were when they were still Woolwich Arsenal was based on the coat of arms of Woolwich, with the three 'posts' in the middle representing the cannons of the artillery based in Woolwich. It was a motif that would remain apart of the crest up until the present day.
In 1922-23 Arsenal started to use a crest that was similar to today's after first introducing the single cannon as the emblem in 1922. It was a west facing cannon, which appeared to be based on the Royal Arsenal Gatehouse in Woolwich even though the Gunners had left Woolwich in 1913.
The next change to the badge came in 1949 with the marksman's motto being included on the badge.
This was the badge that Arsenal more or less stuck with until 2001 when it was tidied up a bit and then again in 2002 when they had to change it due to copyright problems. The only one occasion when Arsenal used a different badge was the 'Art Deco' badge that they used for the 1952 FA Cup final, which they won.
In 2002 Arsenal changed their badge, but it wasn't the usual upgrade that teams tinker with it was due to the fact that as the badge was composed of so many different elements they couldn't copyright it. The main change was that the motto went and the cannon became East facing rather than West.
This season Arsenal have made another change to celebrate their 125th anniversary. The 15 laurels on the left are taken from the 15 sixpence pieces that the 15 original members paid to set up the club and on the right are 15 oak leaves as the members met at the Royal Oak Pub.