Sixty plus years ago I worked a temp job at the register to vote office in our county.
In order to vote you needed to come to the office and fill out a register to vote form and proof of residency. You then raised your right hand and swore allegiance to the USA and were given your card.
On voting day you went to the local grammar school which was the poling place for that area and voted. Your name would be on the list. You were given your ballot and you voted and put your ballot in the ballot box.
Pretty clean, clear cut and legal.