Mo. R. Civ. P. 53.01
A civil action is commenced by filing a petition with the court.
Mo. R. Civ. P. 53.01
Committee Note-1974
This is the same as Rule 3 of the Federal Rules of Civil Procedure with the term "complaint" changed to "petition."
Former Rule 53.01, repealed in 1972, provided as follows:
"Civil actions may be instituted, except when a statute or these rules otherwise provide, either (1) by filing in the office of the clerk of the proper court a petition setting forth the plaintiff's cause or causes of action, and the remedy sought, and by the voluntary appearance of the adverse party thereto; or (2) by filing such petition in such office, and suing out thereon a writ of summons against the person or of attachment against the property of the defendant. The filing of a petition and suing out of process therein shall be deemed the commencement of a civil action."