For much of the latter part of the twentieth century, New York City was a metaphor for the urban decay confronting America’s cities. With murders topping 2,200 in 1990, New York’s jail population was bursting at the seams, peaking at nearly 22,000 in 1991. Few could have imagined that by 2015, the number of murders in the city would have fallen to 350, with steep declines in other crime categories as well. In 2011, University of California Professor Franklin Zimring dubbed New York City’s crime decline ‘‘the largest and longest sustained drop in street crime ever experienced by a big city in the developed world.’’ Given the popularity of incarceration as a crime-control strategy in the United States during this time, a casual mid-90s observer could be forgiven for hypothesizing that, if such a miraculous decline in crime were to occur, it would surely be the result of a massive increase in imprisonment in the city. But quite the opposite turned out to be true. Between 1996 and 2014, the city was bucking the national trends. Its incarceration rate — including inmates in city jails and prisoners in state prisons who originated in the city — declined by 55 percent, while incarceration in the remainder of both New York State and the United States was rising. Despite the fact that the city’s population grew by more than a million people during this time, the number of city residents behind bars declined by 31,120. The city’s reduced use of incarceration has allowed the state to close more than a dozen prisons and save tens of millions of dollars. What allowed the city to reduce incarceration while others increased? In a paper released today, we describe how New York City’s remarkable reversal of mass incarceration was spurred by grassroots advocacy and the rise of responsive and reform-minded public officials at both the local and state levels. Our research reveals two noteworthy findings relative to New York’s incarceration experiment. First, it flowed from — or at the very least, coincided with — a bottom-up effort to amend, repeal, and reverse the laws, policies, and practices that swept our nation into the era of mass incarceration — most particularly those involving the War on Drugs. A successful, sustained campaign to reduce incarceration and abolish the harsh Rockefeller-era mandatory drug sentences was waged by groups like the Prison Moratorium Project, the Correctional Association and the Drug Policy Alliance. Meanwhile, organizations like the Center for Alternative Sentencing and Employment Practices, the Center for Court Innovation, the Center for Employment Opportunities, the Center for Community Alternatives, the Fortune Society, the Osborne Association and the Vera Institute of Justice were providing a network of alternatives to incarceration that is the envy of other cities. While they were at it, both the advocates and the service providers were educating judges, prosecutors, probation officials, policy makers and the general public about the negative consequences of mass incarceration and workable alternatives to locking up New Yorkers. City and state policy makers became increasingly aware of and open to reducing incarceration. A well-publicized Zogby International poll of likely New York State voters found that twice as many were inclined to vote for state legislators who would reduce drug sentences and give judges greater discretion than legislators who would not. State legislators passed a series of laws gradually increasing “merit time” in exchange for program participation; judges and prosecutors diverted more people from incarceration into alternatives; probation officials reduced technical violations; and policy makers funneled a portion of the savings into more community programs. Most notably, the New York Police Department reduced felony drug arrests by 66 percent between 1998 and 2015, even though drug use in the city remained stable during that time. No centralized federal initiative drove this; rather it was the combined work of community activists, service providers and open-minded, or at least persuadable, public officials. While declines in drug arrests were a major driver of population reductions, there was also a 22 percent decline in persons convicted of violent crimes in the city jail system during this time period. These happy trends, which began under Republican Mayor Rudy Giuliani, continued apace under Independent Mayor Michael Bloomberg, and have persisted throughout the current term of liberal Democratic Mayor Bill de Blasio. Our second major finding is that the profound decline in incarceration in the nation’s largest city, which leaves it as one of the least incarcerated cities in America, occurred at a time when New York was also becoming the safest city in America. From 1996 to 2014, serious crime in New York City declined by 58 percent, while it dropped nationally by a more modest 42 percent. By 2014, this left New York City with the lowest crime rate and second lowest jail incarceration rate of the nation’s twenty largest cities. This gives the lie to the notion that more incarceration was needed to provide more safety — a notion that has dominated criminal justice policy in the United States over the last four decades. Several prominent criminal justice reform organizations like JustLeadershipUSA, #Cut50 and the ACLU have urged that the U.S. prison population be reduced by 50 percent. The Close Rikers Campaign is advocating that the city’s jails at Rikers Island be closed, the jail population further reduced and jail facilities located in smaller, neighborhood based sites. It may be tempting to dismiss these goals as unrealistic and unattainable. But New York City’s example shows that when the community and government work together, it is possible to have both half as much incarceration and twice as much safety. Correction: An earlier version of this story incorrectly identified the Center for Employment Opportunities. Vincent Schiraldi is a Senior Research Fellow at the Harvard Kennedy School Program in Criminal Justice and former New York City Probation Commissioner. Judith A. Greene is Executive Director of Justice Strategies.