South Star by Z O Anderson (Paperback)

A team of time travelers believe they have changed history for the better. They return from prehistoric time to a more advanced USA and a better way of life. The team leader wants to go back and correct the paradox and change things back to the way they were, because he wants to time travel back and prevent the death of his daughter. However, one member of the team like the new order and fights to keep it that way. The struggle begins.