Statistics for occurrence #1 of “U. S.” in chapter 5 of Daniel Ammen, Confederate Military History, a library of Confederate States Military History: Volume 7.2, The Atlantic Coast:

... U. S.
Early in the morning of January 31, 1863, two ironclad vessels, known afterward as the Palmetto State and the Chicora, buil...
Max. Freq. Min. Freq.
Entity Corpus Doc Corpus Doc  

† 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.