In 1600, Naomasa II who was the lord of Takasaki-jo Castle in Kozuke Province with properties bearing 120,000 koku (1 koku was about 180 liter; an old unit showing volume) and was one of Tokugawa-shitenno (four generals serving Tokugawa Ieyasu), received an additional properties bearing 60,000 koku due to his distinguished war service in the Battle of Sekigahara, entered into the Sawayama-jo Castle which used to be the residential castle of Mitsunari ISHIDA, and established the Sawayama Domain.
慶長5年（1600年）上野国高崎城主で12万石を領していた徳川四天王の一人・井伊直政が関ヶ原の戦いの戦功により18万石に加増され、石田三成の居城であった佐和山城に入封して佐和山藩を立藩した。