Students who attended the rally said they were flummoxed by the decision, which many learned about through social media posts and text messages, since classes had ended for the semester.
"He loves Morgan. I can see it," said senior Janelle Stewart, 22.
Construction of new buildings picked up under Wilson, she said, and he made decisions popular with students, such as extending hours at the library and cafeterias.
"I think he should have had at least a decade," said Stewart, a sociology major.
Her friend, Corey Ashmore, a 24-year-old senior scheduled to graduate next fall, questioned how a new president, or an interim president, would affect his final semester.
"I don't want anything to change in the transition," he said.
Wilson's ouster marks the third shake-up in recent months in the city's public higher-education institutions. Reginald S. Avery, the president of Coppin State University, announced in October that he would be stepping down in January. This week, Baltimore City Community College's board announced that it was immediately terminating the college president, Carolane Williams.
Unlike Wilson, both Avery and Williams had been under fire for some time and had received votes of no confidence from faculty.
It remained unclear Thursday whether the Morgan board could be forced to revisit its decision.
In an email sent to students and staff Thursday, the University Council said that according to the regents' bylaws, "In order for the Board's vote not to renew President Wilson's contract to be binding and final, it must be made in an open session."
A spokesman for Maryland Attorney General Douglas Gansler said Assistant Attorney General Elena Laingrill was present at the meeting and believed that the regents did not violate the state's open-meetings act.
The meeting was posted on the board's website, which is the "usual and customary" manner in which such meetings are announced, said David Paulson, Gansler's spokesman. No one has filed a complaint with the state's open-meetings compliance board about the meeting, he said.
However, Paulson said, the attorney general's office could not speak to whether the board had violated its own bylaws.
The University Council planned to send a letter to Gov. Martin O'Malley, who appoints the regents, and several other campus groups were compiling correspondence and petitions to send to the governor.
"We'd certainly like to hear their concerns," said Raquel Guillory, a spokeswoman for the governor.
Wilson said Thursday that the board had not told him why his contract had not been renewed. He reiterated his commitment to the university and frustration that he had barely begun to implement his 10-year plan for Morgan.
"I am humbled and honored we have this kind of support," he said. "I am fighting for Morgan."