The VA tracks veteran residency by state. As of last September, it estimates that no state was home to more veterans than California — which makes sense, given the size of the state's population.
Veteran population of each state
The darker the color blue, the higher the population.
Veterans as a percentage of the state population
The darker the color orange, the higher the percentage of the state's population that are veterans.
Notice that Montana jumps out on this map, with ten percent of its population holding veteran status. It may not be a surprise, then, that one of the senators that quickly called for Shinseki's resignation was Sen. John Walsh (D-Mont.). (Walsh is also in a very tough fight to hold the seat he was appointed to earlier this year.) He was joined, we'll note, by Rep. Scott Peters, Democrat of California.