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"Grain loading at country elevators has slowed to a point where the Soo Line is experiencing its first surplus in many months of freight cars normally used in this service. 'It is the first let-up we have had in demand for freight cars for country loadings since 1972,' Soo Line President Leonard H. Murray said. Grain loadings in April decreased with a resulting surplus of both covered hopper cars and box cars used in grain service. As a result, many of these cars are being used to move other commodities, with the bulk of them going into potash service."
Source: The July 1974 issue of Progressive Railroading