April 23, 1919, the opening session of the Estonian Constituent Assembly is the birthday of the Estonian Parliament.[1] The first elections to the Riigikogu took place in 1920. From 1920 to 1938, there were five more elections to the Riigikogu, but several were on the basis of different constitutions. In 1920–1923 there was a closed list, while from 1926 to 1934 there was an optional open list choice.