Were Genders Ever Separated at Catholic Mass?

Yes. It was a fairly common practice in many Catholic cultures into the mid-20th century. Though the 1917 Code of Canon Law did not require separation of men and women at Mass it did recommend it (canon 1262 §1). The 1983 Code makes no mention at all of this practice.

The practice is ancient. It is explicitly mentioned in the 4th century by St. Cyril of Jerusalem and St. Augustine. It most likely was inherited and carried over from the same practice of the ancient synagogues.

Many older churches have a St. Joseph statue on one side of the main altar and a Blessed Mother statue on the other side as a remnant from when this practice was more common. Some older churches even have all the images of male saints on one side and female saints on the other.

The practice appears to have been common in some areas and not in others. It would be difficult to call it a universal custom but it was most certainly not uncommon.