I do my best to see every major historical site and especially those related to US Presidents whenever I have the time in a new city. Having recently read "Destiny of the Republic" it was fortuitous timing to find myself in Cleveland and it's multiple Garfield sites (check out the tomb/memorial site if you're going here as well).
The Garfield National Historic Site in Mentor is well worth a visit. Our tour guide was great, his knowledge obvious and the grounds are beautiful. The house itself and the exhibits within are fascinating.