But, the rise in dangerous and lethal attacks is forcing them to become more secure fortresses.
In just the last two years alone, there have been 16 violent attacks on places of worship. Since 2000, there have been 3,195 violent attacks on houses of worship, hitting a peak in 2014.
The High Holy days, for every faith, put police on particularly high alert, because terrorists know they can inflict optimum damage and loss of life.
At St. Patrick's Cathedral in New York City, uniformed officers and automatic rifles greet worshippers. And, following the Sri Lanka Easter bombing, Gov. Andrew Cuomo, D-N.Y., announced an effort to step up security.
"During these troubling times, we will not be intimidated by cowardly acts of violence and will continue to do everything in our power to ensure the safety of all New Yorkers," Cuomo said.
Congress wasted no time reacting, either.
"These terrorist attacks are a stark reminder that Christians remain the most persecuted and targeted religious group in the world," said Sen. Ted Cruz, R-Texas, "and that we must redouble our efforts to combat religious persecution."
Across the country, though, many houses of worship lack resources and knowledge about security. Many are unaware that there are millions of dollars in homeland security grant money that can help fund protection efforts like personnel training, security cameras and metal detectors.
FEMA has a one-stop-shopping website to give religious leaders information on how to make their buildings and worshippers more secure.
One security expert said while prevention may be difficult, steps can be taken to minimize the risk of attack. For instance, the members themselves could be an extra layer of security.
Steve Padin of Watchmen's Academy said: "Part of that line of defense are the ushers and the greeters. They can come in and they can always welcome people with a smile and with the handshake and just had that welcoming environment right there. But also their job is to just watch things that seem a little bit off."
Alert parishioners may have thwarted a worse scenario in San Diego over the weekend when they spotted what appeared to be an emotionally disturbed woman who walked into the church toting an unloaded gun and carrying a baby.
The other line of defense is to try to prevent an attack from happening in the first place.
"I tell houses of worship that the outside of the facility needs to be monitored either through camera or else by actual people out there," Padin said, "because they can usually spot incidents right from the exterior and prevent something from that to escalate."
The security threat for High Holy days is not over. The Jewish Passover continues through sundown Saturday. And millions of Orthodox Christians throughout the world and here in the United States, are just beginning their Holy Week and will celebrate Easter this coming Sunday.