In my edition of Messages and Papers, here’s part of the essay on Andrew Johnson, which gives the standard view of him in the 1920s.
“In integrity of purpose, in personal and moral courage, in intensity of patriotism he has no superior among our Presidents. That his impeachment marks one of the most dangerous epochs of American history there can now be no question among people whose opinion is at all worthy of respect. Even intelligent Republicans now take this view of the matter. Not long since in a lecture before a college in this city, Mr. Justice John M. Harlan, of the Supreme Court of the United States, stated that as his opinion. He is certainly a competent witness. . . .
If a true history of the United States is ever written, while Andrew Johnson will not stand in the front rank of American statesmen, he will unquestionably stand in the front rank of American patriots. He did more, and risked more, to preserve the Union that was done by all the men combined who voted for his conviction.”