The Hugo Award pages carry lists of winners and nominees but for the early years of the award full lists of nominees aren’t always available.
So for Hugo history nerds here is some news. The 1956 page now has nominees listed as per this announcement. http://www.thehugoawards.org/2017/09/1956-hugo-award-page-updated/
“Thanks to new information coming to light, we have updated the 1956 Hugo Award history page with the finalists that appeared on the ballot that year. We thank Olav Rokne for bringing to our attention an article on page 15 of the 1956 Worldcon Progress Report 3 that included the names of the finalists along with voting instructions.”
The listing was found here http://fanac.org/worldcon/NYcon/w56-pr3.pdf