NEW YORK >> He was the billionaire businessman and untested politician who took charge of a scarred city and steered it into a new era, shaping a New York that projected glittering prosperity, governmental innovation and cosmopolitan confidence.

Michael Bloomberg will be highlighting, and answering for, that legacy in his newly launched Democratic presidential campaign as “a doer and a problem-solver.”

Over 12 years as mayor of the nation’s largest city, Bloomberg governed with a focus on functionality and a vision of New York rebounding from the trauma of 9/11 to become safer, shinier and more of a magnet than before.

The Democrat-turned-Republican-turned-independent (now turned Democrat again) was unbeholden to the city’s Democratic power structure or the combative law-and-order conservatism of predecessor Rudy Giuliani. But Bloomberg’s City Hall wasn’t without ideology of its own: data-driven; tech-friendly; committed to making national waves on gun control, public health and climate change; unapologetic and unafraid of backlash if officials were confident they’d be proven right in the end.

The approach did much to transform the city. But many New Yorkers were chafing as Bloomberg’s tenure neared its 2013 end, in a third term he’d won after engineering a term-limits-law change.

Some felt Bloomberg’s New York worked better for a well-off elite than for others, including hundreds of thousands of black and Hispanic men experiencing police “stop and frisks” each year, the homeless whose numbers had surged, the tenants who rued seeing rents rise along with pricey skyscrapers. The term-limited mayor’s successor, Democrat Bill de Blasio, told a campaign “tale of two cities” that resonated with voters who felt Bloomberg was out of touch.

Nonetheless, Bloomberg left office with nearly two-thirds of voters saying he made the city better, according to a Quinnipiac University poll, and a long list of important mayoral moments.

Here are some.

June 12, 2002: The school takeover.

“I commit to you today that I will make the schools better,” Bloomberg said when an education overhaul he muscled through the Legislature became law in 2002.

He had campaigned on gaining control of the nation’s largest public school system, troubled by low test scores and high dropout rates. It was overseen by an unwieldy combination of an appointed board — which Bloomberg said ran the schools “like a rinky-dink candy store”— and 32 elected school boards.

After getting control, Bloomberg left his mark by championing charter schools, expanding school choice, giving schools letter grades, and replacing scores of struggling institutions with clusters of small schools. His presidential-campaign announcement boasted that he gave teachers “the largest raise in America” and improved high school graduation rates by 42%.

Many of his education initiatives were contentious. Protests erupted when some schools closed. Bloomberg’s choice system gave families options, but was criticized as fueling segregation by expanding the number of schools allowed to screen students by test scores, interviews and auditions.

JULY 1, 2002: The cigarette tax.

Six months into his tenure, Bloomberg signed what he said “may be the most important measure my administration takes to save people’s lives.”

It raised the city’s cigarette taxes to the highest level in the nation.

Bloomberg went on to prioritize public health, banning smoking in bars and parks, making chain restaurants post calorie counts and prohibiting artificial trans fats in restaurant food. He lobbied food manufacturers to use less salt.

Then, in 2012, Bloomberg took aim at soda.

Pointing to rising obesity rates, he proposed a 16-ounce cap on non-diet soda and other sugary beverages sold in restaurants and other venues.

Health officials praised the first-of-its kind measure. Industry groups and believers in laissez-faire called it unfair to businesses and condescending toward consumers, dubbing the mayor “Nanny Bloomberg” and “Mayor Poppins.”

Courts struck the measure down.

Bloomberg called the outcome “unfortunate” but remained proud of his public-health record, saying his administration’s biggest accomplishment was a roughly 3-year increase in residents’ life expectancy.

MAY 15, 2006: The gun crackdown.

Saying he wanted to stanch gun violence at the source, Bloomberg announced in May 2006 that he was suing 15 dealers he accused of selling firearms illegally — in other states.

“Efforts to stop this bloodshed have to reach across state lines,” said Bloomberg, whose administration said the shops were linked to guns used in New York City crimes.

The lawsuits resulted in court-appointed monitoring for many targeted shops and a burgeoning role for Bloomberg as a public face of gun control.

He went on to co-found Mayors Against Illegal Guns — now part of his Everytown for Gun Safety advocacy group — and has given millions of dollars to pro-gun control candidates.

Critics complained he was deaf to the views of millions of firearms owners.

The National Rifle Association caricatured Bloomberg as an octopus on the cover of its magazine in 2007. A Virginia group organized a taunting “Bloomberg Gun Giveaway.”

DEC. 3, 2007: A subway line extension, and growth.

A rail yard on Manhattan’s Far West Side had been a linchpin of Bloomberg’s bid for the 2012 Summer Olympics. After it failed in 2005, Bloomberg pivoted to reconceiving the 28-acre area as a new neighborhood of offices, apartments, arts spaces and more.

To facilitate it, the city took an unusual step to finance a subway line extension.

The December 2007 groundbreaking for the city’s first additional subway station in a quarter-century was a milestone in the city’s biggest private real estate development since Rockefeller Center.

Hudson Yards, which opened this March, was part of the roughly 40 percent of the city that was rezoned during Bloomberg’s tenure.

Bloomberg said his administration created or preserved more than 175,000 affordable housing units. But for many New Yorkers, affordability slipped from reach.

By 2013, some 54% of renter households were spending 30% or more of their income on housing, up from 43% in 2000, according to New York University’s Furman Center. The number of people in homeless shelters rose about 60% during Bloomberg’s tenure, despite his pledge to reduce homelessness by two-thirds.

Bloomberg insisted he had worked to fight poverty. Yet he was unabashed about also courting the rich.

“That’s where the revenue comes to take care of everybody else,” he told New York magazine in 2013. “Wouldn’t it be great if we could get all the Russian billionaires to move here?”

AUG. 3, 2010: The mosque speech.

When a proposal to build a Muslim community center near ground zero generated a bitter debate over tolerance and the legacy of 9/11, Bloomberg delivered one of the most impassioned speeches of his career.

When first responders rushed to save people on Sept. 11, 2001, he noted, “not one of them asked, ‘What God do you pray to?’”

“Muslims are as much a part of our city and our country as the people of any faith, and they are as welcome to worship in lower Manhattan as any other group,” he said.

The terror attacks happened two months before Bloomberg won the mayoralty, partly by arguing that his business experience would help revitalizing the city.

Bloomberg at times alienated some Sept. 11 victims’ relatives, but he also led the development of the ground zero memorial.

As progress stalled in 2006, Bloomberg joined the 9/11 memorial foundation board and became chairman to boost fundraising, giving at least $15 million of his own fortune. Organizers credited him with injecting momentum. The memorial plaza opened in 2011, followed by the museum in 2014.

OCT. 29, 2012. The superstorm.

Superstorm Sandy slammed New York City with a surge of water that killed 44 people and plunged swaths of the city into darkness. Flooding damaged tens of thousands of homes, swamped subways and forced evacuations of hospitals and nursing homes.

Bloomberg offered a voice of on-top-of-it assurance.

“We will get through the days ahead by doing what we always do in tough times — by standing together,” he said.

Those days were packed with problems: enduring outages, gas shortages, senior citizens stranded in high-rises where elevators didn’t work.

Bloomberg embarked on home-repair initiatives that drew initial praise for performing basic fixes on 20,000 dwellings in five months, but led to yearslong delays for more substantial repairs.

He also proposed a $20 billion plan to protect New York with levees, flood gates and other defenses.

AUG. 12, 2013: The stop-and-frisk strike down.

During the Bloomberg administration, civil rights groups went to court to end the NYPD’s use of a tactic known as “stop and frisk,” which involved detaining, questioning and sometimes searching people deemed suspicious by officers.

A federal judge’s 2013 ruling on the program was unsparing: The police had violated thousands of people’s civil rights.

“The city’s highest officials have turned a blind eye to the evidence that officers are conducting stops in a racially discriminatory manner,” U.S. District Judge Shira Scheindlin wrote.

The tactic was longstanding, but its use soared under Bloomberg and then-Police Commissioner Raymond Kelly, from about 97,000 stops in 2002 to a high of almost 685,000 in 2011.

They argued the tactic helped drive crime down to record-low levels, but only about 10 percent of stops yielded arrests or summonses.

De Blasio later dropped the city’s appeal of the ruling, agreeing to reforms and a court-appointed monitor.

Bloomberg apologized for this month for supporting stop and frisk.

“I can’t change history,” he told a black church congregation in Brooklyn, but “I realize back then I was wrong.”