I think the first was John quincy Adams, hence i just edited my post... yes eisenhower was as well! Theres actually several though who were over 50% bald which supposedly constitutes a bald head.
Heres a video i found on a quick search, but if you look for Trump doing the ALS challenge and you can see once he gets soaked that its his real hair. I believe he mentions it in there as well. Its been such a conspiracy for so long that nobody seems to know the truth, lol.