The more than 2,000 markers that adorn Pennsylvania roads and sidewalks arise from nominations submitted by people and organizations, which also bear the financial cost.
For each person, place, or thing Morello nominates, she undertakes an arduous, one-at-a-time effort to compile supporting research and find a financial backer.
"Her commitment is really remarkable," said Richard Sand, who serves on the state Historical and Museum Commission, which runs the marker program. "She does it because she understands how meaningful this is to the community. It opens all their hearts."
Sand, a Philadelphia lawyer, stood on a Walnut Street sidewalk on Thursday, among 50 people who helped dedicate the latest of Morello's triumphs: A marker honoring Old St. Joseph's Church and the Rev. Joseph Greaton, who in 1729 established the foundation of Catholicism in Pennsylvania.
After the official unveiling, which included the Rev. Daniel Ruff dressed in the garb of a 1700s-era clergyman, several people approached Morello to thank her. It was her fourth Catholic church.
She also was the force behind the marker at the Italian Market. And the zoo. And the old Moyamensing Prison, now site of an Acme Market. And one that honors the native son who made Philadelphia a punch line - W.C. Fields.
Her favorite? Maybe the marker at 4548 Market St., outside what is now the Enterprise Center. Back in the day, it was the TV studio from which American Bandstand became a national obsession.
That marker was special, Morello said, because the show bridged the country, bringing East Coast fashion and culture to the West.
That nomination, like others, required 40 to 70 pages of supporting paperwork.
"We certainly have individuals or groups that submit marker nominations every year, or pretty much every year, but not over the period of time or with the amount of success as Celeste," said Karen Galle, the state's historical marker coordinator. "She's become very savvy at submitting successful nominations."
This year, the museum commission approved a marker, among others, for the Bryden Horse Shoe Works in Catasauqua, recognizing a factory that supplied what in the 18th century was a military necessity. In Latrobe, a plaque will honor Fred McFeely Rogers and his children's TV show.
The state gets about 50 nominations a year, but only one of every three or four is approved.
Of course, not all of Morello's nominations are winners.
"I've had a lot of duds," she said. "Some places have been denied three times."
She's tried to get a marker to recognize the Mischianza, an elaborate party thrown to celebrate British Gen. William Howe in Philadelphia in 1778, but a five-year search for a financial sponsor has gone nowhere.
The smaller, city-scale markers cost $1,400; the larger roadside style is $1,875. The price of installation and local permits also is borne by the sponsors.
Morello said that even with nearly 40 successes, she's not the all-time marker champion. That would be her friend Charles Blockson, the scholar of African American history. He's responsible for more than 100, she said.
Her quest began 20 years ago, when she wondered whether anyone besides her noticed the markers around the region. She asked the museum commission what groups or times were underrepresented - generally 19th-century Irish, Italian, and Jewish immigrants - then started doing research.
"It was a release for me, and a balance to the work I was doing in crime history," Morello said. "At the same time I was doing organized crime and homicide records, I was able to feel good about honoring somebody."
She lives in Philadelphia but grew up in Norristown, reading every book she could find. She later earned degrees from Chestnut Hill College along with a master's in history from Villanova University and a second master's in criminology from St. Joseph's University.
She taught in Catholic schools, sold real estate, gave tours for the National Park Service. She's written three books on the Philadelphia Mafia and another on St. Paul's Church.
Today she lives on savings, pursuing history as a full-time job.
When she began her research on Old St. Joe's, she wasn't sure a marker would be approved for the venerable church. But as she dug, she found riches, learning how the church thrived through the freedom of religion granted by William Penn.
She has two dedications set for September, one for Commodore John Barry, a father of the Navy, the other for Mathew Carey, a friend of Benjamin Franklin and early Philadelphia publisher.
"It's remembering these people for what they did," Morello said. "Somehow in the course of the cosmos, somebody shines down on these people to make these things happen, and it propels civilization."