By Zach Carmosino, news correspondent

“Can you imagine being there for 15 years and not going crazy?” human rights advocate Susan McLucas asked an energized crowd on Park Street on Saturday.

Fifteen years after the Bush administration opened the Guantánamo Bay detention camp, Boston activists rallied Saturday to close the prison. About 20 people gathered outside the Park Street Massachusetts Bay Transportation Authority station and chanted phrases like “justice delayed is justice denied” while holding signs with slogans including “end indefinite detention,” “American gulag” and “stop torture.”

The Guantánamo Bay prison has tortured inmates and detained them without trial. Former President Barack Obama promised to close the prison during his 2008 campaign but was met with strong bipartisan opposition. In January, President Donald J. Trump signed an executive order to keep Guantánamo Bay open indefinitely.

Marilyn Levin of United for Justice With Peace, an organization whose website says it was formed after the Sept. 11 terrorist attacks to promote global social justice, said that the land should be returned to Cuba because it is unlawfully occupied by the United States. The United States seized Guantánamo from Cuba 115 years ago in the wake of the Spanish-American war, and it has been under U.S. occupation ever since.

“Guantánamo is illegal because it seizes land from a sovereign country and refuses to give it back,” McLucas said.

Levin said the prison was established to fuel capitalism and is rooted in racism, citing Trump’s vague rhetoric regarding the prisoners as evidence.

“Trump says, with no evidence, that these are ‘bad, dangerous people’ that should not be brought on U.S. soil for trial,” she said.

Nancy Murray, a former education director at the American Civil Liberties Union of Massachusetts, a state chapter of the national organization founded to defend civil rights, said the prison will continue to receive funding from the U.S. Department of Defense. According to the American Civil Liberties Union, this will cost roughly $11 million per detainee each year.

“The cost of keeping it open is truly astounding,” Murray said.

McLucas, a member of the Committee for Peace and Human Rights, said torture is not the solution to stopping forces that threaten U.S. security. She wants to see more peaceful solutions in dealing with detainees.

“We want to return it to Cuba,” McLucas said. “We haven’t gotten anywhere with torture.”

Murray said the time has come for the United States to end its foreign occupations, which currently include territories like Guam, American Samoa and Puerto Rico.

“I propose that our country stop trying to control the world and live peacefully,” Murray said.

Levin said the continued operation of Guantánamo Bay is a power play by the United States to exert power on an international platform. She said this could have dire consequences on the international perception of the United States.

“Bases are used to control,” Levin said. “More people end up hating the U.S.”