We check this website, now gilderlehrman.org is up and dont blocked for our system and other users of the Internet.
So, answer to question: Is gilderlehrman Down Right Now? - NO! gilderlehrman is up!
If you have problem with access to site gilderlehrman, and domain gilderlehrman.org is not avalible.
Clear browser cache and/or try other web browser
(Chrome, Firefox or Safari).