History of Irish Dance
The roots of irish dance

The earliest traces of Irish dance can be found in the circular dancing of the Druids which remains in some of the ceili dancing still practiced today. The Celts living in mainland Europe during the 3rd century spread to Ireland and parts of present day United Kingdom, but retained their native culture which included their dances. During the Viking, Germanic, and Roman invasions many manuscripts were destroyed so little is know about early Irish dancing; however the Book of Kells (medieval manuscript) and architecture knotwork designs can be seen on the clothing worn by stepdancers today.
Feisianna were around at this time. They were cultural and political gatherings. Crafts, sports, music, and dance were all part of these fairs.
In the 12th century after the Anglo-Norman conquest many conquered Irish villages began dancing the Norman dance called "the Carol". The Carol was danced around a singer to which the dancers in a ring around the singer replied with different verses.
tudor to Elizabeth... the irish continued dancing

In the 16th century three dances were mentioned in writings, they were the "Rince Fada or Fading where two lines with partners faced each other, Irish Hey (possibly a round or figure dance), jigs (likely in a group), Trenchmores (described as a big free form country dance), and sword dances. It is not clear whose dances influenced whom among the Irish, English, and French, but it was characteristic that Irish dances had a faster tempo and included side steps." (Anne Robinson website). At this time dances were performed in great halls and castles. The Hey was a dance in which female partners weaved in and out of their male partners which was similar to an early reel. Bagpipes and harps were common instruments heard when dancing.
One of the first references to dance is in a letter written by Sir Henry Sydney to Queen Elizabeth I in 1569. "They are very beautiful, magnificently dressed and first class dancers," Sydney wrote of the girls he saw dancing enthusiastic Irish jigs in Galway (irelands eye website).
Dancers often greeted the arrival of royalty. "When King James landed at Kinsale, County Cork, in 1780, he was welcomed by dancers. Three people stood abreast, each holding ends of a white handkerchief. They advanced to slow music and were followed by dancing couples, each couple holding a handkerchief between them. The tempo of the music increased and the dancers performed a variety of lively figures." dancers would also dance at wakes around the deceased (irelands eye website). Weddings, christenings, and holidays were also popular times to dance.
Dancing takes shape
Dancing masters were becoming common during the 18th century and traveled around within districts from village to village instructing new pupils. Each master stuck to their district, but sometimes villages would get a different master by any means. At fairs masters would challenge eachother till fatigue or the person who knew the most steps ended the dance.
Group dances were developed so that the less skilled students would enjoy dancing as well. Solo steps were prized and doors were sometimes used as stages for dancers to dance upon. Solos steps did not arise till the latter 18th century.
Ceili dances began sometime before the famine in Ireland and got their start at the crossroads. In summer months people would gather at the crossroads to dance on Sunday evenings
Modern irish dancing
In 1893 the Gaelic League (Conradh na Gaeilge) was founded after years of oppression of Irish culture and dwindling number of Irish dancers. "In 1929, the Irish Dancing Commission was founded (An Coimisiun le Rinci Gaelacha) to establish rules regarding teaching, judging, and competitions. It continues in that role. Prior to 1929, many local variations in dances, music, costumes and the rules of feisianna existed. Part of the impact of the Commission was standardization of competitions." (Anne Robinson website)
Now in modern dancing more movements are possible than historically because stages no longer are confined to crossroads and doors. Girls before the 1920s were not unusally seen dancing in competitions, now they are more predominate. Soft shoes were introduced around 1924 males also wore them sometimes till the 1970s.
If you want to learn more about the history of Irish dance clothing check out these two good posts on the dance.net Irish boards:
http://www.dance.net/topic/6166678/1/Irish-Photos-Misc/Reely-Old-Irish-Dance-Photos.html
Here are some links referenced above to see the full text or learn more about the history:
Dance as if no one were watching!