高田藩
He became "daimyō" of Takada Domain in Echigo Province (100,000 koku) on the death of his father in 1618. However, only one year later, he was transferred to Matsushiro Domain in Shinano Province by order of the shogunate, with the same nominal "kokudaka". Three years later, in 1622, when the shogunate dispossessed the Mogami clan, Tadakatsu was transferred again, to become "daimyō" of Shōnai Domain. At that time, his "kokudaka" was increased to 138,000 "koku". One of his first actions on becoming "daimyō" of Shōnai was to begin the construction of Tsuruoka Castle as a replacement for the dilapidated Kamegasaki Castle. However, the completed Tsuruoka Castle was given to his grandson, Sakai Tadayoshi, and he continued to reside at the old Kamegasaki Castle after his retirement. It was unusual for a domain, especially of this size, to have two castles in violation of the shogunate's "one domain - one castle" edict, and was a mark of the high standing the Sakai clan enjoyed within the shogunate. On the other hand, funding of this castle resulted in higher taxation, which caused unrest in the domain, even to the point where petitions were sent directly to the shogunate in Edo in 1634 complaining about misgovernment.