Back in November, activists met Richmond Mayor Dwight Jones with heckles at the formal unveiling of his proposal to build a baseball stadium in Shockoe Bottom. Five months later, the opposition has become more strategic, intense and widespread.

The past two weeks have seen the launch of an organized ballot initiative to scuttle the plans and a smattering of national and international attention, with the family of Solomon Northup — the subject of the Oscar-winning film “12 Years a Slave” — coming out in opposition. Should all else fail, activists say they’ll turn to civil disobedience.

“The bottom line is, we’re ready to be arrested trying to stop the construction,” says Phil Wilayto, an organizer of the activist group Defenders for Freedom, Justice and Equality. Seven people have committed to blocking construction.

But Wilayto and others hope it won’t come to that, they say, and they’re encouraged by recent events.

The Solomon Northup Foundation issued a statement Friday on behalf of Northup’s descendants.

Northup’s book describes how he was trafficked through a Richmond slave jail operated by William Goodwin. Its location is a matter of some dispute, with different historians placing it in the center of the proposed stadium location or along the perimeter. The precise site is secondary to Northup’s family.

“It’s just amazing to me that this area hasn’t already been preserved,” says Clayton Adams, the executive director of the foundation.

In a three-page statement, Adams, who is the third great-grandson of Northup, says it’s the family’s goal to come “together as one voice … to produce a stronger call for preventing the construction of a baseball stadium.”

“For many African-Americans,” Adams writes, “the ability to trace ones’ descendants has already been made difficult due to the longevity of slavery here in this country. But with the preservation of the Shockoe Bottom District … this very real connection to those family histories can make this difficult task seem less impossible.”

Adams, who lives in Pittsburgh, says he learned about debate in Richmond after another relative of Northup, Linsey Williams of Fredericksburg, launched a petition for family members opposed to the project. Williams is scheduled to speak at 6 p.m. April 3, at the Lumpkin’s jail site at 15th and Grace streets.

The Northup descendants’ petition was the subject of articles last week in The Hollywood Reporter in Los Angeles and The Guardian, a British newspaper.

Local opponents hope the site’s connection to Northup’s story will help others understand their opposition and, in turn, generate more national attention.

The mayor’s press secretary, Tammy Hawley, says the Northup family’s concerns are misplaced: The stadium will provide for the memorialization of the area’s slave history. “We agree that historic places should not be unseen and left unheard,” she says in an email, “and that is why our plan is a comprehensive plan preserving the burial grounds and creating the Slavery and Freedom Heritage site.”

Adams and Williams say they’re unmoved. “It’s insensitive to consider building a baseball stadium in that area,” Williams says. “I can’t speak for everyone because I haven’t heard from everyone, but the family members I have spoken to agree.”

The people behind the ballot initiative want to solidify support among a local demographic: registered voters. The effort’s engineer, former state Democratic Party Chairman Paul Goldman, says the group needs to collect signatures from 9,800 voters by August to make the November general election ballot.

City and state law don’t provide a mechanism for a binding referendum, so the measure attempts to stop ballpark construction in a roundabout way. It changes the city charter to create a historic review commission to review the project. And it lowers the number of council members needed to call a nonbinding, advisory referendum on stadiums and arenas from five to three. City Council President Charles Samuels had proposed calling for such a referendum last summer, but it died on a 6-3 vote.

City Council is likely to make a final decision on whether to go forward with Jones’ ballpark proposal this summer — well before the November election, but Goldman says that doesn’t concern him. “Even if they vote for it, they’ll still have a lot of money to appropriate over the next few years,” Goldman says. “They’ll try to say it is too late, but it’s not.”

Goldman, a lawyer who ran against Jones in 2008, has the distinction of orchestrating the city’s most recent successful ballot measure, which led to implementing the current mayor-council form of government. His latest attempt came out of a series of meetings with activists held Saturdays at the Richmond Public Library.

The group of about 20 has begun collecting signatures. No matter the outcome in November, they expect its thousands of signatures to have an impact.

“Council will pay a lot more attention to these registered voters than they will normal petitions that anybody can sign and council tends to scoff at,” says Marty Jewell, a former City Council member involved in the drive. “That will be a huge indication of the will of the people.”