Is there a way to know? The highest I've seen is 116k but I'm sure there is a way to know this. I'm just going to keep writing because the thing on my right won't let me post this question without more writing.
If you go on the main site and click on users, you see them ranked by reputation. Click on one of the possibilities week/month/quarter/year/all to select the range from which you want see the reputation. If you click on all, you will see the users ranked by the total reputation.
You can find some interesting information also in reputation leagues. For example, you can find top users in some given year or month. Or if you are curious who were the top ranked user at the end of previous years, you can find this information, too: 2014, 2013, 2012, 2011, 2010.