Page "Siddur" Paragraph 6

The earliest existing codification of the prayerbook was drawn up by Rav Amram Gaon of Sura, Babylon, about 850 CE.

Half a century later Rav Saadia Gaon, also of Sura, composed a siddur, in which the rubrical matter is in Arabic.

These were the basis of Simcha ben Samuel's Machzor Vitry ( 11th century France ), which was based on the ideas of his teacher, Rashi.

Another formulation of the prayers was that appended by Maimonides to the laws of prayer in his Mishneh Torah: this forms the basis of the Yemenite liturgy, and has had some influence on other rites.

From this point forward all Jewish prayerbooks had the same basic order and contents.