Before becoming the 26th president of the United States, Theodore Roosevelt Jr. cut his political teeth in his boisterous home state of New York—maneuvering his way from the state assembly to the New York City police department to the governor’s mansion. From the start, he followed his progressive impulses to fight corruption, temper unfettered capitalism and lift up the less privileged. And he wasn't afraid of making enemies in the process.

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Roosevelt’s political journey to the White House began inside the Manhattan brownstone in which he was born in 1858. A member of one of New York City’s wealthiest families, young Teddy was profoundly influenced by his father, a revered philanthropist who contributed to charities for orphans and homeless newsboys and taught Sunday school. “His father taught him that with great wealth came great responsibility,” says Richard Zacks, author of Island of Vice: Theodore Roosevelt's Quest to Clean Up Sin-Loving New York. “The Gilded Age was the most obscene flaunting of wealth the country had ever seen, and Roosevelt was appalled by that.”

With little interest in amassing more wealth, the future president shunned the business world after graduating magna cum laude from Harvard University in 1880. He instead shocked friends by choosing a career many considered beneath his upper-crust pedigree: politics. “It merely meant that people I knew did not belong to the governing class and that the other people did—and that I intended to be one of the governing class,” he recalled.

Three years after his father died, the 23-year-old Roosevelt became the youngest man ever elected to the New York State Assembly. His progressive streak was apparent from the start of his political career. The upstart legislator investigated a judge for taking bribes from Wall Street financier Jay Gould, supported improved conditions for cigar factory workers and targeted corruption with municipal and civil service reform bills, even those opposed by his party. Always a whirl of energy, Roosevelt was called “the cyclone assemblyman” by the press, which quickly learned that he made for good copy.

Tragedy struck when his beloved mother and wife, who had given birth to their first child two days earlier, passed away just hours apart in the same house on Valentine’s Day in 1884. “The light has gone out of my life” were the only words he could summon for his diary. Three days after the double funeral, Roosevelt returned to Albany and poured himself into legislative work, moving 21 bills out of committee in a single day. “I think I should go mad if I were not employed,” he confided to a friend.

The devastated Roosevelt, however, refused a nomination for a fourth term. Placing his new daughter in the care of a sister, he fled New York and sought solace in the solitude of the remote Dakota Territory, where he became a cattle rancher.

READ MORE: 7 Little-Known Legacies of Teddy Roosevelt

Roosevelt returned to New York City in 1886 and ran for mayor, but the “cowboy candidate,” as the press dubbed him, finished third in a three-way race. Unsure of his political future, Roosevelt penned a series of books. “I’m a literary feller not a politician these days,” he wrote in 1888. But not for long. A year later, he accepted an appointment to the U.S. Civil Service Commission in Washington, D.C., where he targeted political patronage while serving both Republican and Democratic presidents.

An appointment to New York City’s police commission in 1895 drew Roosevelt back to Manhattan. Given a mandate to reform a police force awash in bribery, Roosevelt removed corrupt law enforcement officers and conducted “midnight rambles” to check that city cops were making their rounds. Sometimes joined by the press and photographer and social reformer Jacob Riis, Roosevelt saw firsthand how the “other half”—the poor and foreign-born—lived. “My whole work brings me in contact with every class of people,” he wrote to his sister. “I get a glimpse of the real life of the swarming millions.”

To tame a city teeming with vice, Roosevelt re-instituted the daytime use of the nightstick, which had been previously removed for its brutality, and armed policemen with a standard gun. He attempted to enforce all the city’s laws, including one that prevented the sale of alcohol on Sunday but was flagrantly flouted thanks to the bribery of police officers and political machines by saloons. Roosevelt didn’t necessarily agree with the law—thinking it “altogether too strict”—but he believed it his duty to enforce it.

The attempt to shutter Manhattan’s 15,000 saloons on the sabbath angered many, particularly German immigrants who frequented them on their one day off. Tens of thousands protested Roosevelt in street rallies, and two pipe bombs were mailed to him. “I would rather see this administration turned out for enforcing laws than see it succeed for violating them,” he wrote, undeterred.

He left the job after 15 months to make whistle-stop campaign speeches for the Republicans’ 1896 presidential candidate, William McKinley. “This is the last office I shall ever hold,” he predicted to a friend. “I have offended so many powerful interests and so many powerful politicians.”

Roosevelt’s unique combination of progressive and law-and-order credentials, however, positioned him for higher office and proved popular across the country. “He earned a law-and-order reputation from what he did in New York,” Zacks says. “And he played it up and congratulated himself in speeches about cleaning up the country’s most corrupt city.”

After serving as assistant secretary of the Navy and organizing the Rough Riders to fight in the Spanish-American War, the self-proclaimed hero of San Juan Hill returned to New York—and state politics. Elected governor in 1898, Roosevelt signed nearly 1,000 bills into law, including those that taxed corporations, limited working hours for women and children, preserved forests and improved sweatshop conditions.

Roosevelt’s refusal to hand out patronage jobs and his support of taxation bills, however, chafed the state’s Republican Party boss, Thomas C. Platt, whose political machine had put him in office. Unable to control Roosevelt, Platt conspired to move him out of the governor’s office by maneuvering him into what Roosevelt considered a useless position—vice president of the United States. “Ironically, Roosevelt ultimately succeeded by making himself so obnoxious to the greedy, corrupt and powerful that they booted him upwards to get rid of him,” Zacks says.

Roosevelt reluctantly agreed to accept the nomination as McKinley’s running mate in the 1900 election. “This election tonight means my political death,” he lamented after McKinley won a second term.

Less than a year later, after McKinley was assassinated by a gunman at the Pan-American Exposition, the 42-year-old Roosevelt became the youngest president in American history. He took the oath of office, fittingly, in his home state of New York.