A lot of effort in discrete maths / combinatorics is expended in the construction of lists, catalogues or census [sic] of combinatorial objects such as groups, graphs, designs etc. These catalogues are now a fundamental part of computer algebra systems.
Obviously nowadays most of this is done by computer, but a surprisingly large amount of this work predates (electronic) computers - for example, G.A. Miller worked on creating lists of "substitution groups" (permutation groups) in the late 1800s and early 1900s, while Ronald Foster created the "Foster Census" of cubic symmetric graphs in the 1930s.
I'd like to know some more examples of famous "cataloguers" of mathematical (well, particularly combinatorial) objects predating electronic computers.