This period of history held the largest gap for me, and I imagine I am not alone. The Civil War ends, Reconstruction begins. The gap goes until the Spanish American war followed by WW I. In the gap, we have the corruption in the Grant administration, the betrayal of Reconstruction by Rutherford Hayes, the reassertion of white supremacy in the South, the continued denial of voting rights to women, and significant European immigration. We also see the rise of the ultra wealthy captains of industry, controlling much of transportation and manufacturing. There is emergence of some worker's unions and other coalitions to challenge the wealthy.
The development of the Republican party from its anti-slavery roots into an advocate for limited government takes place, while the Democrats continue to struggle for definition, always seeming to be based in the South but forming coalitions, eventually resulting in the election of Grover Cleveland as the first Democrat since Andrew Johnson. The history of abuse and destruction of both native Americans and African-Americans are shameful. There is a development of an American ethos that is rather fatalistic. That is, the poor are responsible for their poverty. Sweat and determination brings wealth and power. Never mind that there are few if any examples of women or minorities that become powerful.
Government is recognized as uniquely capable of some achievements, most conspicuously military annexation of land. As commerce becomes more international, protective tariffs are debated as helping and hurting. There are many instances of financial booms and busts, and the country struggles with fiscal policy to address problems.
Perhaps the most fascinating aspect of the book is the description of the rise and presidency of Woodrow Wilson. His story reminds including context reminds me of the present day with Elizabeth Warren in the role of Wilson.