Thanks Patty and Jami for your quick answers!
I'd like to share that I found this ftp site that contains historical population estimates including the vintage one:
www2.census.gov/.../ It takes a bit a dig and find in the layers of folders to get the data I look for, but it worked!
The NHGIS is a very neat site with a lot of historical information indeed, but just does not have the population component piece I was looking for. I will definitely come to NHGIS for my later research!
Thank you guys! Have a wonderful New Year!