What are some curriculum that used to be secular, but isn't anymore?

I'm curious. The only ones I'm aware of are Ambleside, and Friendly Biology (originally started with a secular biology big book for high school level, but then later revised it into a Christian world-view, which I think is so strange to do). Horizons has a secular K-5 package but not their 6-8 levels are only Christian. TumbleBooks started one way and later added the other, but I dont know if they were Christian or Secular at first.

I hope this curiosity doesn't kill the cat.