Thousands of people all over the U.S. are expected to rally against gun violence Saturday alongside the students of Marjory Stoneman Douglas High School for the “March for Our Lives” protest.

The student survivors of the Parkland, Florida massacre have been planning the March 24 rally since shortly after the shooting at their high school on Valentine’s Day that left 17 dead. Officials in Washington, D.C. — where the main March for Our Lives rally is taking place — are preparing for roughly 500,000 people to attend the march, according to the Washington Post. In addition to bolstering subway service throughout the day Saturday, there will be also be a heightened police presence.

“We will ensure that we have plenty of officers on hand to facilitate a peaceful and safe day for the rally,” Washington, D.C. Police Chief Peter Newsham told Voice of America.

Satellite March for Our Lives protests are also happening from coast to coast Saturday, including in major cities like New York City, Los Angeles, Portland and Chicago.

Here’s everything we know about the upcoming March for Our Lives, including details about marches in various cities, how the march got started and which celebrities are planning on joining the students on March 24:

When is March For Our Lives?

March for Our Lives is taking place on March 24, 2018. In Washington, D.C., the march will begin at 12 p.m. (E.T.).

Where is March For Our Lives?

March For Our Lives has a central march in Washington, D.C. that will begin at noon at Pennsylvania Avenue, between 3rd and 12th Street NW. There will be pedestrian entrances at Pennsylvania Avenue and 12th Street, NW; Constitution Avenue and 7th Street, NW; and Indiana Avenue and 7th Street, NW. There is a downloadable map at the March for Our Lives website.

March For Our Lives starting point Google maps

For those taking the metro, the Washington Metropolitan Area Transit Authority (WMATA), suggests purchasing metro cards (SmarTrip) in advance; the WMATA also has other trips for travelers at their website. There “could be a record-setting day” for transportation in the city, according to the Washington Post. The metro will be operating at rush hour frequency on Saturday starting at 7 a.m. local time.

Organizers are also taking safety precautions, with a list of items not allowed at the march in D.C. — from coolers and drones, to toy and real firearms. They also want people to be mindful of their rally signs. “Please do not mount signs on wood or metal sticks or posts as they will not be allowed in,” the website warns. “Poles and posts will also not be allowed on the metro.”

In addition there will be food trucks, available water, medical tents, portable toilets (including ADA accessible toilets), and both pedestrian and accessible entrances to the march, according to the March for Our Lives D.C. info page.

What if I’m not in D.C.?

Much like the Women’s March or the March for Science, satellite marches have popped up around the globe (you can find more information about at the March For Our Lives website).

So far, according the March for Our Lives organizers, there are over 800 marches being planned — including in Los Angeles; Chicago; Miami; Las Vegas; Springfield, Missouri; San Francisco; Dallas; New York City; Birmingham, Alabama; West Palm Beach, Florida; Boise, Idaho; Liverpool, England; and more.

The march in Downtown Los Angeles march will begin at 9 a.m. local time and will start at 603 S. Spring Street.

A march planned in New York City will be held in Manhattan at 10 a.m. local time, and will start at Central Park West at West 72nd Street.

In Boston, the march will begin at 11 a.m. local time at the Madison Vocational High School.

Chicago’s march will begin at 11 a.m. local time and will start at Union Park.

Who is funding March For Our Lives?

The organizers have started the March for Our Lives Action Fund, which along with paying for the expenses associated with the Washington, D.C. march, will “be used to fight for comprehensive gun safety legislation at the local, state, and federal level, and will also include voter education, ballot initiatives, and lobbying state legislatures and Congress to protect America’s kids,” according to the March Four Our Lives FAQ.

The March for Our Lives organizers have already raised more than $3 million on GoFundMe, which will be split between the Action Fund and the Broward Education Foundation to support families of those killed or injured in the shooting.

Celebrities are also donating to the cause. George and Amal Clooney gave $500,000 to March For Our Lives, which was matched by Oprah Winfrey, Steven Spielberg and Kate Capshaw, and producer Jeffrey Katzenberg and Marilyn Siegel. Ellen DeGeneres and Shutterfly announced on DeGeneres’s talk show that they’d making a joint donation of $50,000, and Chrissy Teigen and John Legend pledged $25,000.

The Italian fashion brand Gucci also donated $500,000, according to The Hollywood Reporter, and Axios reported that Josh Kushner (brother of President Donald Trump’s son-in-law Jared Kushner) donated $50,000 to the cause.

The Miami Heat’s Dwane Wade and actress Gabrielle Union said they’d donate $200,000 to the March For Our Lives efforts. Carmelo Anthony also said he’d be donating, and they encouraged other players to as well.

Parkland, Florida student Joaquin Oliver, who was killed during the Marjory Stoneman Douglas shooting, was buried in Wade’s jersey.

The organizers are also spreading the word about others who are attending the march:

On the March For Our Lives website, Everytown for Gun Safety and Giffords Courage were mentioned in reference to “assisting in the coordination of sibling marches around the country.”

In February, BuzzFeed reported that Women’s March Los Angeles co-executive director Deena Katz submitted a permit application with the name “March For Our Lives” in the “individual/organization” section. It’s unclear if this is the actual permit for the march. TIME reached out to the Women’s March Los Angeles for more information.

“A spokesperson for Women’s March Los Angeles confirmed that Katz is helping to organize the gun control march, and submitted the permit application in an individual capacity,” BuzzFeed reported in February. BuzzFeed also wrote that, “The Women’s March is not involved in the event, the spokesperson said.”

On the Women’s March Los Angeles website, the organization explains, “While we work on some of the same issues in conjunction with Women’s March on Washington group, we are separate entities.”

Who is attending March For Our Lives?

A wide range of celebrities have endorsed March For Our Lives, and some will also be in attendance.

“We’re gonna have four major independent women that are standing with us and walking beside us, and those are Ariana Grande, Jennifer Hudson, Miley Cyrus and Demi Lovato,” Marjory Stoneman Douglas High School student and activist David Hogg told CNN this week. “They’re gonna be standing there with us and marching with us and they’re some of the few people that are really coming out and stepping up with us.”

More notable artists have also been added to the lineup, including Common, Andra Day, and Vic Mensa.

Chef José Andrés has also announced a #FoodForOurLives partnership to feed high school students coming to the march.

Late-night host Jimmy Kimmel told the students of Parkland, “I’ll marching alongside you with my wife and two children in D.C. to show our support.” George and Amal Clooney also said they’d be marching; and comedian and activist Chelsea Handler also tweeted that she’ll be there, as did actress Julianne Moore.

Many celebs have also tweeted about the march, pledging their support by signing a petition, donating to the GoFundMe or announcing their plans to join the students later this month. This week, late-night host Jimmy Fallon encouraged viewers to support the march.

On Monday, March 19, Tony winners Lin-Manuel Miranda and Ben Platt released the song “Found/Tonight”. Part of the proceeds from the Broadway mashup — which combines Hamilton’s “The Story of Tonight” and Dear Evan Hansen’s “You Will Be Found” — will go towards March for Our Lives.

Why are people marching?

The idea for the march came shortly after the Feb. 14 shooting at the Parkland, Florida high school, where 17 people were allegedly killed by a former student, 19-year-old Nikolas Cruz. Cruz was armed with an AR-15 rifle that he had legally purchased, authorities said.

Cruz was indicted earlier this month by a grand jury on 17 counts of both first-degree murder and attempted murder. He appeared in court last week (the same day that students walked out of class to call for gun control), where a “not guilty” plea was entered by the judge on his behalf, as he stood silent during the hearing. Earlier in March, his lawyers filed papers to withdraw his “not guilty” plea. “Assistant Public Defender Melisa McNeill said in the filing that Cruz ‘stands mute’ before the court,” according to the Associated Press.

Marjory Stoneman Douglas High School students have been quick to demand action following the shooting — visiting the Florida state capital and meeting with lawmakers, while planning the march in Washington, D.C. from their parents’ living rooms. The March for Our Lives has since expanded to include other major cities across the U.S. From New York City to Los Angeles.

And the students of Marjory Stoneman Douglas have already seen results from their actions. The Florida State Legislature passed an expansive gun control measure that includes banning bump stocks, raising the age to purchase a firearm across the board from 18 to 21 (before you needed to be 21 to purchase a handgun, but could be 18 to purchase a rifle or shotgun), institutes a three-day waiting period on gun purchases, and providing more funding to school safety and mental health resources. The bill was signed into law by Gov. Rick Scott. On March 14, the U.S. House of Representatives passed the STOP School Violence Act that, while it doesn’t address gun control, appropriates more money for school safety, training, and tip lines.

“We can’t ignore the issues of gun control that this tragedy raises,” one of the high school organizers Cameron Kasky wrote in an op-ed for CNN. “And so, I’m asking — no, demanding — we take action now.”

Are the marches Republican or Democrat?

While issues around gun control often fall along party lines, the student organizers goal, according to their website is school safety, which they say “is not a political issue.”

“There cannot be two sides to doing everything in our power to ensure the lives and futures of children who are at risk of dying when they should be learning, playing, and growing,” according to their mission statement. “The mission and focus of March For Our Lives is to demand that a comprehensive and effective bill be immediately brought before Congress to address these gun issues.”

What other protests are planned?

March for Our Lives is not the only protest being planned by students. In addition to a nationwide school walkout earlier this month, the students are also planning National High School Walkout on April 20 — the 19th anniversary of the Columbine shootings.

This isn’t the first time survivors of mass shootings have organized. Moms Demand Action for Gun Sense in America sprang up after the Sandy Hook Elementary School shooting that killed 20 students and six staff members. In 2001, Columbine survivors successfully lobbied Kmart to stop selling ammunition. In a gut-wrenching scene in Bowling for Columbine, survivors Mark Taylor and Richard Castaldo went to Kmart headquarters to show the bullets still lodged in their bodies. They said all the bullets were purchased at a local Kmart.

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