When Washington debates whether America is safe, the focus now is usually on the increasing threat of terrorism - not violent crime.

That has largely obscured some good news about violent crime: Across the nation, homicide rates have dropped to their lowest levels in nearly a generation. And overall violent crime has sunk to its lowest level since 1973, Justice Department statistics show.

The reductions have continued despite a grinding recession, a slow economic recovery and spikes in gang membership, according to recently released FBI figures for the first half of 2010.

The long-term trend is particularly striking in the nation's three largest cities -New York, Chicago and Los Angeles. Homicides in New York have dropped 79% during the past two decades - from 2,245 in 1990 to 471 in 2009, the last full year measured. Chicago is down 46% during that period, from 850 to 458. Los Angeles is down 68%, from 983 to 312.

The reductions, especially in New York, have been so dramatic that violent crime virtually has disappeared from the national political discourse.

"It certainly did not emerge in the (November) midterm elections, and it hasn't been an issue of national public concern since at least 2000," Carnegie Mellon University criminologist Alfred Blumstein says.

Analysts say a range of factors have helped to tamp down violent crime. Among them: improved crime-mapping technology that has allowed police to deploy officers more efficiently at a time when many law enforcement resources are being directed toward anti-terror programs; crackdowns on gangs and community outreach programs that are being credited with thwarting serious crimes.

And then there have been factors beyond the control of police: a booming economy for much of the past two decades, and the absence of gang-fueled wars over a drug of the moment, such as the turf battles over crack cocaine that led to unprecedented urban violence in the 1980s and '90s.

For all the good news, in America's three biggest cities the two-decade free-fall in homicides has not erased public insecurity about violent crime. The prospect of prolonged economic woes raise troubling questions about whether violent crime could rise again, and some recent trends that affect residents' quality of life have been unsettling.

Julie Menin, chairwoman of New York's community development board representing Lower Manhattan, says the jump in violence and the threat of new terror attacks have created a "heightened level of anxiety" among residents, despite the public safety gains of the past two decades.

"The (overall) numbers are encouraging," Weis says, "but we still have a lot more work to do."

"The perception of safety is always going to be at odds with the reality of it," Los Angeles Police Chief Charlie Beck says.

William Bratton, a New York-based security executive who led the New York and Los Angeles police departments during some of those cities' steepest drops in violence, says he believes the nation is experiencing a fundamental decline in violent crime.

Bratton says a key factor is that there is no potentially "cataclysmic" drug epidemic on the horizon similar to that of crack cocaine, which he and other analysts say fueled the widespread street violence of the late 1980s and early 1990s. Reductions in violence, he says, have been sustained despite the post-9/11 shift in law enforcement resources from fighting street crime to stopping terrorism.

"I don't see (homicide and other violent crime) ever returning in the numbers we once saw," Bratton says.

New York's 'in-your-face' system

In the well-worn corridors of the NYPD's 71st Precinct in central Brooklyn, the "wallpaper" gets changed most every day, sometimes hourly.

The unusual decor is a montage of computer printouts of charts and maps that track every major crime in the densely populated, 2-square-mile neighborhood of Crown Heights.

Police Inspector Peter Simonetti says the "in-your-face" surveillance system - part of which the public can access online - is at the heart of the precinct's and the city's success at reducing violence for much of the past two decades.

"The immediate access to information about where crime is has helped tremendously," says Simonetti, the precinct's husky commander.

On the walls, a constellation of inkblots mark the scenes of the most recent slayings, robberies, burglaries, rapes, assaults and gun crimes. The detailed mapping system helps police identify troubled areas so commanders can redirect officers and, hopefully, prevent additional and more serious crimes.

As the NYPD's commissioner in 1994, William Bratton introduced the evolving policing philosophy known as CompStat. It has spread to several U.S. cities, including Philadelphia, San Francisco, Boston and Los Angeles.

One wall inside Simonetti's office is devoted almost entirely to gun crimes. Through November, police have recovered 82 illegal guns from neighborhood streets, resulting in the arrests of 104 suspects. That number is up from 52 guns and 82 arrests at the same time in 2009.

"How many of those guns could have been used in murders later?" police Lt. Steve Weiss says.

Despite this year's uptick in violence, Police Commissioner Ray Kelly says the city "just feels much safer" than a decade or two ago.

"I don't think there is universal appreciation for the scope of the reduction" in murder and other violent crime, the commissioner says, in part because of the threat of terrorism, which is more acute in New York - scene of the World Trade Center attacks on Sept. 11, 2001- than any other city.

He calls this year's jumps in homicides and rapes "anomalies."

"There is nothing to indicate that this rise is going to continue," Kelly says. "When you have 8.4 million people together, you are going to have some people who kill each other."

Julie Menin, a community board chairwoman in Lower Manhattan, says New Yorkers worry about both the terror threat and the public's potential vulnerability as the police department shrinks.

Since 9/11, Kelly says, the department has lost 6,000 officers to retirements and attrition, but its anti-terrorism and public safety responsibilities have increased. With about 35,000 officers, it remains by far the country's largest police agency.

"I think it's only natural to look at that (decline in officers) as a reason why we're seeing violence tick back up," Menin says.

In Chicago, not everyone feels safe

Jessica Hanson isn't worried about becoming a homicide victim.

She moved to Chicago from Indiana four months ago for a marketing job and used an online crime-tracking site to choose a North Side neighborhood that has occasional burglaries and car thefts but no slayings so far this year.

"I absolutely feel safe, even at midnight," says Hanson, 25.

Fifteen miles south of Hanson's condo, Tearra Betts-Montgomery, 38, and her three daughters moved to a house in Englewood, one of the city's deadliest neighborhoods, 10 months ago.

"You can't walk out of your home feeling safe," she says. "You can't carry purses, you can't wear certain colors. If you're out doing your yard, you may be shot. ... If you hear a gunshot, hit the floor. That's what I tell my kids."

Despite a dramatic decline in homicides since 1990, fear still permeates some Chicago-area neighborhoods. The city is on track to end 2010 with fewer homicides than in 2007, which had the lowest total since 1965. The success comes despite a drop in resources: At the end of 2007, there were 11 police vacancies; by Dec. 31 there will be at least 950. The total force now is about 12,700.

A 2009 analysis found that almost all of Chicago's shootings and homicides occur in 8.5% of the city's 227 square miles, Police Superintendent Jody Weis says. A recent spate of child slayings and the overall numbers - 412 people killed through Nov. 30, compared with 424 in the same period last year - stir concern that the entire city is dangerous, he says.

"It is unacceptable in any city in America," Weis says, "that more than one human being is murdered a day."

Chicago police are finding new tools that target the gangs responsible for about 60% of homicides. A new predictive analytics group uses computer algorithms that factor in weather and other variables to predict where and when crimes will be committed so patrols can be adjusted, Weis says. About 800 officers can move swiftly to areas where violence erupts.

Yet aggressive police work can't fix all root causes of homicides, says Arthur Lurigio, a criminal justice and psychology professor at Loyola University Chicago. "We have to address intergenerational disenfranchisement and poverty. Your view of risk in the community is not based on crime statistics; it's based on your everyday life experiences."

A big change in Los Angeles

After living in one of the toughest, gang-ridden sections of Los Angeles for nearly 30 years, Max Sanchez doesn't need statistics to know street violence is down.

"You don't hear all the gunshots at night anymore," says the truck driver, 42, who moved to South Central Los Angeles with his family in 1982. "Now we can be outside, even if it's nighttime."

No one is saying violent crime has been eradicated in Los Angeles, where decaying neighborhoods gave birth to street gangs such as the Crips, Bloods and others that have infused pop culture with inner-city "gangsta" imagery.

Yet from luxury condos and other signs of revitalization that are changing a once-seedy downtown, to the relative quiet of Sanchez's neighborhood 70 blocks to the south, a dramatic downturn in homicides and violence is reshaping this city and the lives of many of its 3.8 million residents.

Police Chief Charlie Beck says he expects the city to have fewer than 300 homicides this year, a low not seen since the 1960s and fewer than half of the 654 killings eight years ago. It is roughly one-quarter of the number of killings during the bloodiest period of gang and drug wars. The violence peaked in 1992, with 1,094 killings. Among the factors Beck and others cite for the decline:

Few places are more linked to Los Angeles' violent reputation than the area near the police department's 77th Street station in South Central. For officers there, such as Sgt. Paul Shearholdt, each day brings reminders of the dramatic drop in violence - and that some threats remain.

A ride through his beat shows the work of gangs that tag buildings with elaborate graffiti to mark their turf. The markings help cops detect power shifts among gangs, Shearholdt says.

There have been 31 slayings in the 77th Street division's area in 2010, down 11% from 2009 and 26% from 2008. In the early 1990s, there were more than 150 killings a year in the 12-square-mile area. A few years ago, Shearholdt recalls, it was common for cops to hear gunfire on patrol, turn a corner and find a body. Now, it's rare.

"It's amazing," says Beck, once an officer in the division. "That place is changed forever."