Mornings on Horseback seems to have cemented McCullough's style and reputation as the dean of American historians. This book follows the young Theodore Roosevelt, from his ancestors to the start of his second marriage in 1886. It is, as the phrase goes, "a life intensely lived." The Roosevelt were New York aristocracy, and young Teddy was coddled by privilege; servants, European tours, the best of everything. At the same time, he exerted maximum effort, long marches and rides through any wilderness he could find, hunting and naturalism all bundled up into one, actually working at Harvard and in the New York legislature. Simultaneously, this was also a family stricken by illness and sudden death. Loved ones fall alarmingly fast, and Teddy was suffered from asthma for much of his childhood before finding a psychological cure (in McCollough's estimation).

McCullough hasn't yet figured out how to transmits the complexities of 19th century politics, and the book flags towards the end with the famous ranch in the Dakota Badlands. This is a great portrait of the boy, and excels particularly in showing Teddy in college, but it dearly feels like volume one of a larger project never finished.