The locks will be required by 2003 under the bill approved Monday night by the House. Until then, all guns sold will have to be equipped with external trigger locks, beginning in October.
No other state has approved such a measure. Gov. Parris Glendening is eager to sign the bill, already approved by the Senate.
It will be "a couple of days" before Gov. Glendening signs the bill, reports CBS affiliate WTOP-AM reporter Hank Silverberg.
"This bill takes a giant step toward creating safer communities not just in Maryland but across the country," Glendening said. He predicted that within 18 months, six to 12 states will move forward on similar legislation.
"I predict that it will be almost impossible for gun makers to manufacture guns without internal safety locks. The liability simply will be too great," the governor said.
President Clinton called him immediately after the vote to congratulate him. The president said Maryland's success will inspire other states. At an informal briefing Tuesday morning, deputy White House press secretary Jake Siewert said Clinton also stressed a need for federal action.
"The president believes very strongly that the state efforts are important, but they are not the entire solution," Siewert said. "We can't have the states do this all on their own."
Opponents, representing largely rural and conservative suburban areas, tried 10 times without success to amend the bill in hopes of derailing it. Opponents said the built-in locks would embolden burglars and would-be rapists.
"The bad guys know you're not going to have time to get that lock off," said Delegate Carmen Amedori, a Republican. "I don't want another kid to die, but I don't want more women raped...I don't want my 76-year-old father's home getting invaded."
Emotional speeches from opponents were greeted with thunderous applause from the House gallery above, packed with opponents.
Among other things, the bill would prohibit anyone convicted of a violent crime as a juvenile from possessing a handgun until age 30 and require gun manufacturers to provide a ballistic fingerprint of shell casings of all new handguns. It also imposes five-year mandatory minimum sentences on some convicted felons caught illegally possessing a handgun.
The National Rifle Association has been running television ads attacking the bill since Friday. The 30-second ads feature the governor as he fumbled at a press conference trying to open a push-button combination lock on a handgun.
"If your family's safety is threatened, how much time will you have to unlock the firearm you depend on for protection?" te commercial's narrator asks.
Massachusetts, meanwhile, announced Monday that it would enforce requirements that guns come with safety warnings, tamper-resistant serial numbers and indicators on semiautomatic handguns that show whether a bullet is in the chamber.
The regulations also use consumer-protection rules to ban cheap guns known as Saturday Night Specials and require childproof locks on any gun sold in the state.
Thirty-four other states have passed legislation that would allow them to regulate handguns as they would any other consumer products. Massachusetts is the first to actually impose such regulations.
Proponents of so-called "safe-guns" are watching the Maryland vote closely. They believe after Smith & Wesson's recent agreement to manufacture safer guns, a win in any state legislature gives them powerful momentum.
"This law will save life," says Glendening. "The integral lock that we are talking about will save the lives when a child picks up a gun, looks at it and starts playing because that's what they've seen on television, and goes to shoot and kills a little sister or little brother."
Statistics released Friday confirm that children frequently live in houses with guns. A University of California at Los Angeles-RAND Corporation study shows that 35 percent of households with children have firearms and that 43 percent of U.S. homes with children and guns, a gun is kept in an unlocked place and without a trigger lock.