Ever since Ronald Reagan invited federal bureaucrat-turned-hero Lenny Skutnik to watch his State of the Union, seats in the first lady's guest box above the House of Representatives have been used to honor the best among us. (Skutnik jumped into the icy Potomac River to help rescue a drowning woman in the Air Florida Flight 90 crash 30 years ago.)

Heroes from the Oklahoma City bombing and the Sept. 11, 2001, terrorist attacks, astronauts, teachers, veterans, community leaders and even politicians are among the handful of people invited as the first family's guests to the president's annual address to Congress.

Of course, as with just about anything in Washington, who gets picked is full of political symbolism. Presidents choose guests who can humanize their policies and priorities, notes The Washington Post's Ed O'Keefe.

That's why President Obama's decision to leave a seat empty to honor victims of gun violence is notable. State of the Union guests have become such a time-honored tradition in Washington that Obama is hoping to make a statement with an empty seat the way a filled one never could. At least one other president, George W. Bush, has purposefully left a seat empty; his was in 2003 to honor 9/11 victims.

Here's a look back at some of the people who have filled those seats, and what presidents hoped to convey with their presence.

Ronald Reagan's guests

Besides Skutnik, Reagan filled his guest box at the rest of his State of the Unions with more everyday Americans, such as Trevor Ferrell, a 13-year-old who helped the homeless in Philadelphia, or Mother Clara Hale, a Harlem nun who cared for abandoned children.

Of course, there was at least one notable exception to the rule, below.

Reagan made more State of the Union history in 1986 when he became the first president to postpone the address after the space shuttle Challenger exploded. According to Gerhard Peters, who tracks all State of the Union guests at the American Presidency Project, Reagan invited Richard Cavoli, a private citizen who designed a science experiment in high school that was lost during the explosion of the space shuttle Challenger.

In 1988, Reagan honored his wife, Nancy Reagan, for her drug-prevention efforts, including the "Just Say No" campaign she coined while talking to school children.

George H.W. Bush's guests

Bush only delivered two official State of the Unions, because he served only one term. His guests were almost exclusively related to politics -- education one year and America's military ramp-up the next.

In 1990, Bush wanted to honor governors who helped him develop national standardized education goals for the year 2000. He invited South Carolina Gov. Carroll Campbell Jr. (R), Iowa Gov. Terry Branstad (R), Washington Gov. Booth Gardner (D) and Arkansas Gov. Bill Clinton (D).

No, that's not a typo; Bush welcomed the guy who would later unseat him to the State of the Union.

In 1991, as he launched the Persian Gulf War, his State of the Union guest box took a decidedly more militaristic tone. Bush invited Alma Powell, the wife of Gen. Colin Powell (who then was chairman of the Joint Chiefs of Staff), and Brenda Schwarzkopf, the wife of Gen. Norman Schwarzkopf, who was then leading U.S. forces in the war.

Bill Clinton's guests

Guest lists became much more expansive under Bill Clinton -- and remain so today.

Clinton's guest list over the years included everyone from civil rights icon Rosa Parks to the first Chinese American governor, Gary Locke (D-Wash.) to baseball greats Hank Aaron, and Sammy Sosa to world-champion science students.

For his first official State of the Union in 1994, Clinton invited Jim Brady, Reagan's former press secretary who was shot during an attempted assassination on the president and recently died, more than three decades later, as a result of the shooting. Clinton celebrated the 1993 signing of the Brady Bill requiring federal background checks for purchases from federally licensed gun dealers and called on Congress to approve more gun-control measures.

In 1996, Clinton invited Sgt. Jennifer Rodgers of the Oklahoma City Police Department. Rodgers helped save victims of the bombing of the federal building, and in his State of the Union, Clinton announced Rodgers would be one of the first Americans to carry the Olympic torch to Atlanta for the Summer Games later that year.

George W. Bush's guests

Bush also had a lengthy guest list that, with the exception of his first official address in February 2001, focused heavily on the war on terror.

In 2002, he invited flight attendants Cristina Jones and Hermis Moutardier, who helped thwart an attempted shoe bomb by Richard Reid.

In 2006, Bush invited the parents and widows of Marine Corps Staff Sgt. Dan Clay, who was one of 10 Marines killed by a roadside bomb in December 2005 in Fallujah, Iraq.

Obama's guests

As The Post's Dan Lamothe and Juliet Eilperin note, Obama's guests in 2016 tell the story of his tumultuous presidency. He's inviting a Syrian refugee, one of the first women to be the first to finish Army Rangers school (in celebration of the military opening all combat roles to women) and a plaintiff in the Supreme Court case to legalize same-sex marriage.

You could say the same for past Obama State of the Union invitees as well. He has invited people affected by the 2008 banking crisis, self-starter immigrants, soldiers and people who he says are positively affected by his 2010 health-care reform law, known as Obamacare.

In 2011, he invited Peter Rhee, the lead doctor who treated Rep. Gabrielle Giffords (D-Ariz.) at Tucson University Medical Center just days earlier when she was shot point-blank at a rally.

And to drive home Obamacare, he invited Jim Houser, owner of Hawthorne Auto Clinic in Portland, Ore., whom he met a few months earlier. Houser's business employed 15 people and he paid the entire cost of their health-care coverage.

In 2015, he invited newly freed Alan Gross. The federal contractor was imprisoned in Cuba for five years and released after Obama announced a month earlier a historic thawing of relations with the island country.