"If we allow these attacks to divide us, and if we allow the terrorists to cause us to violate our most cherished principles of fairness, justice and the deep respect for civil liberties, then the terrorists will have won," said Jamal Said, imam of the Mosque Foundation.
But Muslims in Chicago and elsewhere said they also felt a special duty to reach out to people of all faiths to reaffirm the message that the attacks run counter to Islam.
Members of the Islamic Cultural Center of Greater Chicago joined fellow Northbrook residents for a candlelight vigil on the village green. Parishioners of Old St. Patrick's Catholic Church accepted an invitation to attend prayers at a Chicago mosque.
"Now is a time for us to look outward, and Sept. 11 has made it more critical that we do it right away," said Mansoor Ahmed of the Islamic Center of Naperville, who planned to participate in a joint service with a Lutheran church.
More than two dozen members of Old St. Patrick's, some wearing head scarves out of respect, sat in chairs at the Downtown Islamic Center while about 80 Muslims sat on the floor after the afternoon zuhr prayer. The two communities have held interfaith gatherings since the fall.
Mohammed Kaiserrudin, the mosque's president, said he appreciated words of support and acts of kindness by President Bush and friends of all religions. But he also spoke out against "hateful words" spoken by some against Islam and "the loss of civil liberties" of individuals and Muslim organizations.
"Our lives have been changed forever," Kaiserrudin said.
Participants from both communities said the interfaith ceremony held special significance on a day of memorial services everywhere.
Old St. Patrick's parishioner Katy Ryan, 39, said she was moved by the Daley Plaza commemoration earlier in the day. But praying with Muslims, she said, "takes it to another level. It's about building relationships."
Mansoor Panawala, 22, added: "It's more important since guests are coming to let them know that we as American Muslims mourn the event. This is not something we tolerate and accept."
Imam W. Deen Mohammed, spiritual leader of the Muslim American Society, whose members are primarily African-American, also condemned the attacks, during a unified prayer service in Harvey.
"There is no sympathy for those who have lost their humanity. There can never be sympathy for suicide bombers," he said.
More than 100 Muslim centers nationwide signed up for a "Day of Unity" organized by four prominent Islamic advocacy groups, which encouraged participants to hold open houses and public events at mosques.
At the patriotic ceremony in Bridgeview, which featured a 21-gun salute, Said implored residents to come together. Nearly a year ago, police stopped a flag-waving mob from marching on the mosque.
Christian leaders who attended affirmed the need for understanding by encouraging residents to read books to learn about Islam.
A delegation of Muslim students from the Universal School mingled in the crowd. Some incorporated American flags into their head scarves. Hani Ali, a 17-year-old senior, said he was "glad people realize that we are all Americans."
Later, pupils sat on prayer rugs in the school's gym at an assembly to mark the anniversary. Alaa El Sheikh, a 2nd grader, recited from the Koran: "Surely with difficulty is ease. With difficulty is surely ease."
Like a coach at a pep rally, principal Safaa Zarzour encouraged students to channel their grief into a determination to make Muslims a "source of healing, bridge-building and kindness." He also urged them to confront fellow Muslims who violate those principles.
"Guess whose responsibility it is to teach the world and show them the true face of our religion?" Zarzour said. "It is our job to go out and make that clear."
Tribune staff reporter Bonnie Miller Rubin contributed to this report.