Most sights especially in the earlier muzzle loading firearms were rather low profile.
This was in an effort to keep them from being knock about.
These arms were also rather slow loading between shots, so the rifleman didn't need to worry about the barrel heating up like one will find in later types of raped shooting firearms.
However, as hunters moved out onto more open country like the plains, they found that having a rear sight that could be easily adjusted for greater distance quickly would be to their advantage.
My best,
Blair