It is a nice use-case to be able to query for the abci state a few blocks ago, or at least to be able to specify the same block height for multiple queries to get a consistent snapshot even if the block progresses in the meantime. Jae also thinks this is very important for removing race conditions from ibc-like communication.

This was at one time considered part of #355 but ended up a much bigger project, and that "just" got proofs from the present block (which already was a huge improvement). Now that historical queries should soon be supported in go-merkle, I want to create this issue to remind us to expose this thoughout the whole stack - merkleeyes, abci, tendermint. So that a client can get a proof of the state from a few blocks ago.