There are a few different more-or-less interactive maps of the Inner Sphere and the larger BT universe to be found scattered across the interwubbs. However, I've never found one that has any way of seeing changes in borders (worlds that were conquered from one faction to another) aside from pulling up versions of the map at different time junctures and eyeballing them side by side. You'd have to spend a substantial amount of time switching between browser tabs or combing through multiple sources to find a complete list of, say, all the worlds the Capellans lost to the FedSuns in as major a canon event as the 4th SW.
Are there any resources that make it easier to find worlds matching certain criteria on change of control? Like for example, if I wanted to find a Lyran world that gets taken by the Combine by 3025 but ISN'T one of the 50-some the LC takes back in the 4th SW?