Which state saw the largest creation of reservations within its borders

The answer is California.

According to most recent census data, there are more than 100 separate reservations or Rancherias in California. 362,801 Native Americans from 109 federally recognized Indian tribes and from 78 additional entities that are asking for recognition, live in these reservations. Indigenous culture, customs, habits, and traditions are still practiced on the Native American reservations.