We've done this in the past four years (in which tournaments were held - although for, um, reasons last year's somehow went unfinished). The more detailed explanation is in the 2018 thread, but the general principle is that each county in the country is assigned to the 68 NCAA tournament teams by geographic proximity (distance from home arena to geographic center of the county) and then the map consolidates as the games are played (winning team takes losing team's land). Only two sets of adjacent territory games in the first round, both in the West region (although one of those is in the northeast of the county): Connecticut-Iona, and TCU against whoever wins ASU-Nevada (technically, TCU is only adjacent to Arizona State - and only along a small sliver of land in northern New Mexico - but whoever wins the play-in game will own the land regardless). Will update this periodically, but hopefully no less often than the conclusion of a day of games.