(originally posted on r/tf2)
What are you talking about
A fact almost nobody knows about this game is that there's a huge compilation of your personal game data in TF2. I was first made aware of this from this TFTV thread. On top of your hidden casual MMR rating, you can also see a complete history of every single (valve official) casual game you've ever played, your end of round survey responses, the exact time and date you played your first TF2 match, how many total games you've played, and so on. As far as I know, TF2, CS:GO, and Portal 2 are the only steam games with such in-depth information about your game history. And if you've ever wondered what was the first map you ever played, you can find it.
Now TF2 is keeping track of my personal data?? Where do I find this anyway?
To see this, go to your steam profile and click on Games. Next to TF2, drop down Personal Game Data and click on [your name]'s Personal Game Data. Clicking on the Match History tab shows you detailed information about every valve casual match you've ever played. This tells you when you joined and left, how many kills/deaths/damage you had, etc. It tells you everything you'd want to know except one thing: the name of the map you played. You can see here that the map name is not in plain English but referred to as a "map index" number. This makes data cleaner on Valve's end, but it tells us nothing.
So what the heck is "Map Index 15"? I've search through the TF2 Wiki, looked inside the BSP map files themselves, and scoured the internet. There didn't exist a single source anywhere for what these map indexes refer to. Until now. I took it upon myself to compile a list of map indexes and what maps they refer to. I painstakingly spent the last few nights joining (bot-filled) matches and checking back to this game data page to see what new map index number popped up. I won't bore you with the details, but this took many many hours. I mean have you seen the list of maps there are in TF2? Skip this next part if you don't care about the details.
If you wanted to be bored with the details though
To my annoyance, not every match was recorded for some reason. Sometimes an entire match would finish and a new record wouldn't show up. I found out that there were only two ways a new record would get updated to this list: 1) at the very beginning of a match or 2) if a placeholder name was added for your current match. If it got updated immediately at the start, I would record the map index and move on. If it didn't, there would be a placeholder game type of "Bootcamp" with a map index of 0. If I saw a new record with this Bootcamp name, I knew I would only get the complete game info after the game was totally finished (it updates right as the win condition is met and you see the server scoreboard at the end of a game). But if I joined a new server and nothing new would show up, I would have to join a new server as the match data would never get recorded and I'd be wasting my time staying there.
I think you're missing a few maps
I left off a few maps because I would never get matched into them, like Hydro or Vanguard or Probed, and some I left off because it was honestly taking too long making this list. The maps I'm missing are plr_bananabay, cp_foundry, cp_vanguard, koth_sawmill, tc_hydro, and some of the other misc maps I've almost never played. And I didn't want to play Passtime or Mannpower. If you want to know the map indexes for those maps, you would have to queue for that map, watch your Match History page for updates, and record the Map Index number once it's over. Anyway here's the full list. I realize this info will be useful to almost nobody, and I only created this because of a handful of posts on this sub asking if there was a way to find the very first map they played on. But with this list, that question should now be answerable.
I couldn't find table formatting on this forum so I'll just post the list as an image:
Map Index List