I am currently reading John Marshall Harlan: The Last Whig Justice by Loren P. Beth, a relatively straightforward, and somewhat dry, biography by a political scientist. Judicial Enigma: The First Justice Harlan by Tinsley E. Yarbrough covers similar ground, as I recall, and was equally average overall. I also own the copy of his wife's memoirs that Justice Ginsburg particularly sponsored, though Beth's book had access to said papers before they were published for general circulation. They were an interesting entry into the mind-set of late nineteenth century women's thought with a few explanatory essays to help us understand them better added as well.
Harlan is an interesting guy, seen as a type of profile in courage for some of his great dissents, especially in the Plessy ruling. It is much remarked that he was a former slaveowner, but provided the most liberal viewpoint on race issues. This is not as amazing as it might seem, once we examine his background. As the title says, he was a "whig" justice. His father was a major whig politician and legal mind in Kentucky, naming another son after Henry Clay. The family had a firm religious faith plus a focus on the law (one of John Marshall Harlan's sons went into the ministry), thus no need for many slaves. No abolitionists, the family were still fairly "liberal" on the race question, if having typical paternalistic/racist sentiments per our view of the matter.
Harlan's politics led to belief in a strong national government (relative to the day), concern for basic fundamental rights, and opposition to secession (he joined the Union side during Civil War, but left when his father died, not taking direct part in any major campaign). The Republican Party, however, seemed too radical on the race question, and he opposed the Emancipation Proclamation and the Thirteenth Amendment. Thus, when the Whig Party fell apart, he was in a bit of a pickle. Though he supported Lincoln's Democratic opponent (a general, after all) in 1864, the Democrats -- especially after the war -- was too much tinged with rebellion for his tastes.
[Kentucky and Delaware, the former having only a small slave class, were the only slave states that were forced by the Thirteenth Amendment to free slaves -- the others by state action passed abolitionist amendments. But, some still retained a belief that state action was the way to go, especially since the second section of the federal amendment provided a possibly broadly open-ended authority for the feds to control local race questions.]
But, besides a lawyer, Harlan was deep down quite the politician. So, he needed a party. Attempts to work the middle failed. This was shown as early in 1860 with the Constitutional Union Party. So, the Republicans beckoned. Many former Whigs went that route, and aside from the race question (which also seemed decided once the Thirteenth and Fourteenth Amendments were ratified -- opposition to them did not mean he could ignore them), the Republicans seemed benign on many issues. Likewise, the Democrats appeared too over the top even on the race question -- supporting anarchy and violence to promote their cause.
[Harlan's paternalistic views also kicked in. Blacks might be inferior, but there was some level of restraint required here. Thus, his wife in her memoirs pointed to a scene in which his father damned slave auctions. Likewise, he risked his life to save a slave who caught on fire. OTOH, his Plessy dissent voiced racist thoughts, such as how the white race will probably remain supreme culturally.
Likewise, though he opposed interfering with voluntary integrated private colleges, his Berea College dissent particularly differentiated public school segregation. Harlan also joined, without comment, a ruling upholding differing penalties for interracial fornication. There were limits, especially in social regulations ... public accommodations were different. Thus, use by some of his words to oppose affirmative action is somewhat ironic, since he himself clearly felt race was sometimes relevant when governmental action was at stake.]
And, once a Republican, Harlan followed the usual route of the enthusiastic converted. Anyway, following in his father's footsteps, he was a partisan (running for governor on the Republican ticket, for instance), and had a strong moral belief system. Firm in his beliefs, Harlan brooked no dissent or haziness of argument. Thus, his Civil Rights Cases dissent, especially since it would upheld democratically passed law, was logical. Ditto his Plessy dissent -- others beforehand had strong Republican backgrounds (e.g., Chief Justice Chase), reflected in their opinions. That is, Republicanism of the Reconstruction Era kind, not the slew of corporate lawyer types chosen during Harlan's time on the Court.
Harlan's decades before his time incorporation of the Bill of Rights also followed the pattern. It arguably was the original understanding of the Fourteenth Amendment, actually. He also mixed some Gilded Age beliefs (support of a "freedom of contract," up to a point) with moderate tendencies (dissenting in Lochner, he avoided Holmes' broad approach to use of "reasonable legislation" philosophy). His background surely didn't prevent his support of the constitutionality of the income tax and acceptance of nationalist regulation of the economy such as dealing with monopolies on the manufacturing level. An "American System" that provided a healthy regulation of a national economy was Whig doctrine.
[Likewise, distrust of big business, trusts, etc., reflected usual beliefs from his neck of the woods. The various corporation minded judges of the era as well as those from big city locales might think otherwise, but a Kentucky lawyer/politican would logically have the views expressed in Harlan's opinions, more business friendly than courts might be these days, but still quite wary of their excesses -- especially, if it was just a matter of upholding reasonable (somewhat tinged by his beliefs) governmental legislation.]
Harlan had a long and productive life, centered on hard work and civic/religious duty, mixed with a certain lightheartedness that made him fun to be around. No perfect person (he had his inconsistencies, sometimes for political reasons), surely, he is rightly seen as worthwhile of study. As a final thought, a few days back, I referenced part of an opinion written by him that basically underlined the right of legislatures to be wrong, if they follow reasonable procedures and do not violate fundamental liberties. It concerns the issue of mandatory inoculations, providing interesting reading on various themes, including equal protection of the law.
The ruling is still good law as are many of his dissents, though not those from the Civil Rights Cases (which were advanced via a somewhat makeweight interstate commerce approach) ... but those should be.