The ACSdownload package for R has functions helping to download and parse raw data files from the United States Census Bureau dataset called the American Community Survey (ACS) 5-year summary file. In particular, this package allows you to obtain all of the block group and tract-level data for any or all US States/DC/PR, rather than one State or one County at a time, for specified variables in specified tables. In contrast, other tools such as the acs package tend to provide more limited subsets such as one US County or State at a time, when working with block group or tract resolution tables, and/or require you obtain a key from Census.
Key functions include get.acs() to download and parse specified data, and various helper functions.
This package is not on CRAN -- install it from Github:
if (!require('devtools')) install.packages('devtools')
devtools::install_github('ejanalysis/ACSdownload')