A 19-year-old with a semi-automatic rifle killed 17 people at a high school in Florida on February 14, sparking rage among parents, students and educators.
The display was laid out on the southeast lawn of the Capitol. A sea of empty shoes also filled the grounds outside the Department of Health in 2016 to represent the millions of uninsured people who die each year from treatable conditions.
The shoes will be donated when the monument is dismantled.
Wednesday's #ENOUGH National School Walkout, organized by the activists who helped plan the Women's March in Washington for the past two years, will begin at 10 a.m. local time (1400 GMT).
Avaaz's website says the group received donations from victims' families, members of the public, and even celebrities. Since the Sandy Hook elementary school shooting in Dec 2012 until now, the math shakes out to roughly 7000 kids (0-17) killed by guns since then.
CBS affiliate WUSA reports that the group based the protest on research from the American Academy of Pediatrics that found approximately 1,300 children are killed by guns each year, or about three every day. A few have threatened to suspend students if they disrupt class by leaving.
The protest was the latest movement from activists groups to call on lawmakers to take steps to curb rampant shooting incidents in US schools.
Organizers of the memorial said the Parkland shooting was the catalyst for creating the memorial.
Tuesday's shoe memorial is reminiscent of a monument on the Danube River near the Hungarian Parliament in Budapest commemorating thousands of people, including Jews, killed by fascists in the 1940s.