Apart from John Dewey, no American educational reformer has been as internationally successful and influential as Helen Parkhurst, the founder of Dalton education. In the 1920s and 1930s, Dalton education was spread throughout the world. At the moment the Netherlands is the country with the highest density of Dalton schools. Almost four hundred elementary schools (five percent of all) are Dalton schools. This historical and theoretical study gives an account of the practice and the theory of the Dalton Plan. Next it discusses the background and context of the Dalton Plan. It also compares the Dalton Plan to other critical and innovative approaches to education. Helen Parkhurst was herself not keen on historical and theoretical exercises. This study shows that historical and theoretical research is interesting nonetheless. It demonstrates the distinctiveness of Dalton education, for instance: *that learning by experience is not the same as learning by doing and that experience doesn't have the same role for Parkhurst as it does for other reformers; *that there are important differences between working with assignments in the Dalton Plan and working with materials in the Montessori Method; *that the Dalton Plan holds efficiency as its main objective, whilst at the same time opposing the efficiency-hype seen at the beginning of the twentieth century; *that the meaning of cooperation in the Dalton Plan is not the same as what we usually mean by this; *that Parkhurst's school as a community distinguishes itself from Dewey's school as a community; and *that freedom in the Dalton Plan is something other than freedom of choice.