Early references for discrete optimization (Apologies if this is misplaced or too broad.  I'm open to suggestions on how to reformulate it.)

I'm interested in tracing back the "ancient" history of max-flow algorithms, and discrete optimization algorithms in general.  Ford-Fulkerson is my straw-man of a starting point.  What were the significant advances prior to that?  How far back can we go while still being able to make a reasonable argument that somebody was working on max-flow?  How about graph algorithms?  How about discrete optimization in general?

I'd also be happy to get references to places where this is discussed.
Usually, Schrijver provides a good source for history. You can look at the following books and an article.


Alexander Schrijver. Combinatorial Optimization: Polyhedra and Efficiency. Springer 2003.
Alexander Schrijver. Theory of Linear and Integer Programming. Wiley 1998.
Alexander Schrijver. On the history of the transportation and maximum flow problems. Mathematical Programming 91(3), 2002, 437-445. http://dx.doi.org/10.1007/s101070100259 
Alexander Schrijver. On the history of combinatorial optimization (till 1960).  Handbook of Discrete Optimization, Elsevier, 2005.  http://homepages.cwi.nl/~lex/files/histco.pdf