Unless I’m mistaken, at the writing of the Constitution the slaves that were counted may not have been citizens, but they were legal residents of the United States.
They were legal residents. Reisdent aliens were also counted. Indians were not.
The counting served as the basis for BOTH representation AND taxation, which was appropriated among the states (up until the income tax) according to the census results.
Only relatively recently (I’d guess 60 years ago, but I’m sure there are three dozen people on the forum who can quote the cases, and hundreds more who could look it up, some of whom have more time than I,) did the Supreme Court really get into details on how states doled out their Federal seats, as well as the state legislature seats. Many state legislatures started off with an upper chamber that was not primarily tied to population—not unlike the federal senate.
As a Lib to explain the 3/5ths Clause regarding Slaves in the Constitution that they always vilify to push their narrative.
They use that number all the time in belittling the Founders of our Nation yet they have no concept that the final draft of our Constitution required negotiating between different factions to Unite the States to form our Union.
You may recall the they were only four fifths a person for the very reason they would change the representation power of Southern States.