Complex sentence: The État's line was 610km while the PO's was 582km, these were the only competing lines in France, this lasted until 1938, date of the creation the SNCF, when the PO line was kept.
Split into simpler sentences: The État's line was 610km while the PO's was 582km. This lasted until 1938, date of the creation the SNCF, when the PO line was kept.