In 1870 he oversaw creation of the Justice Department, its first duty to bring thousands of anti-Klan indictments. By 1872 the monster had been slain, although its spirit resurfaced as the nation retreated from Reconstruction’s lofty aims. Grant presided over the Fifteenth Amendment, which gave blacks the right to vote, and landmark civil rights legislation, including the 1875 act outlawing racial discrimination in public accommodations. His pursuit of justice for southern blacks was at times imperfect, but his noble desire to protect them never wavered.
-- Ron Chernow (Introduction paragraph 2)

Importance: This demonstrates one of Chernow's primary arguments, that Grant was an unparalleled champion of civil rights following the Civil War. It explicitly counters the view that Grant was ineffectual as President and had no significant accomplishments.

Loneliness, ennui, frustration, inactivity—such unsettled feelings always conspired to drive Grant to drink. Luckily, he recognized his alcoholism just as the temperance movement gathered strength, and he embraced this new...
-- Ron Chernow (chapter 4 paragraph 3)