Complex sentence: Federal control of the railroads ended on March 1,1920; when the contracts that had been negotiated while under federal control expired the following year, the ORT had to re-negotiate agreements with the individual railroads.
Split into simpler sentences: Federal control of the railroads ended on March 1,1920. When the contracts that had been negotiated while under federal control expired the following year, the ORT had to re-negotiate agreements with the individual railroads.