Correspondence, site maps. Correspondence between UP engineers regarding construction of rail bridge across LA River. Includes correspondence from L. T. Jackson to H. C. Mann regarding City of Los Angeles contemplation of a river truck speedway in bed of river, cost estimates for bridge designs, correspondence from Lloyd Aldrich, City of Los Angeles City Engineer to L. T. Jackson regarding maximum flow of LA River and clearance required between bridge and calculated high water line. Also includes blueprint of SP and AT&SF connections near LA River, proposed connecting track, general layout of bridge over Los Angeles River on LA&SLRR connection to new Union Station.