Milnor produced his famous link homotopy invariants by studying the
fundamental group of the link complement. Edge homotopy (EH) is a
generalization of link homotopy for spatial graphs, but so far, it has
been difficult to produce an analogue of Milnor invariants for all spatial
graphs. We will study a relation on spatial graphs called "component
homotopy" (CH), and produce Milnor-type algebraic invariants. Since
EH implies CH, these invariants are also edge homotopy invariants.