Comparison of carp (top left) and Euclidean-distance Hierarchical Clustering dendrograms on the data. The presidents are colored according to historical period: Founding Fathers (pink, 1789–1817, Washington to Madison, n = 4); pre-Civil War (gold, 1817-1869, Monroe to Johnson, n = 13); pre-World War II (teal, 1869-1933, Grant to Hoover, n = 13); and modern (purple, 1933-present, F.D. Roosevelt to Trump, n = 14). We consider Johnson to be a pre-Civil War president as he ascended to the presidency following the assassination of Lincoln rather than being directly elected.