Statistics for occurrence #1 of “R. Jackson” in chapter 26 of George Bancroft, History of the United States from the Discovery of the American Continent, Vol. 6, 10th edition.:

... R. Jackson
Virginia Consolidates Union. on the sixth of January, the day on which the Legislature of Massachusetts assembled...
Max. Freq. Min. Freq.
Entity Corpus Doc Corpus Doc  
H. R. Jackson 223 0 19 0 0 user votes
Henry R. Jackson 186 0 38 0 0 user votes
J. R. Jackson 96 0 4 0 0 user votes
R. Jackson 22 2 0 0 0 user votes
R. R. Jackson 13 0 1 0 0 user votes
William R. Jackson 10 0 0 0 0 user votes
A. R. Jackson 7 0 1 0 0 user votes
John R. Jackson 7 0 1 0 0 user votes
Daniel R. Jackson 6 0 0 0 0 user votes
George R. Jackson 4 0 0 0 0 user votes
Vincent R. Jackson 4 0 0 0 0 user votes
T. R. Jackson 1 0 1 0 0 user votes

† This entity has been selected by the automated classifier as the most likely match in this context. It may or may not be the correct match.