The National Mall has often drawn massive crowds for presidential inaugurations and rallies and other celebrations. But estimating large crowds on the National Mall is a notoriously tricky business. See photos of large crowds on the National Mall.

Use the scroll bar in the middle of the photos to compare the inauguration crowd sizes of Barack Obama’s first and Donald Trump’s. This pair of photos shows a view of the crowd on the National Mall at the inaugurations of President Barack Obama, right, on Jan. 20, 2009, and President Donald Trump, left, on Jan. 20, 2017. The photo and the screengrab from video were both shot shortly before noon from the top of the Washington Monument. (AP Photo) Use the scroll bar in the middle of the photos to compare the inauguration crowd sizes of Barack Obama’s first and Donald Trump’s. (Associated Press) People stand on the National Mall to listen to the 58th Presidential Inauguration for President Donald Trump at the U.S. Capitol in Washington, Friday, Jan. 20, 2017. (AP Photo/Patrick Semansky) AP/Patrick Semansky Spectators fill the National Mall in front of the U.S. Capitol on Jan. 20, 2017 in Washington, DC. In today’s inauguration ceremony Donald J. Trump becomes the 45th president of the United States. (Photo by Alex Wong/Getty Images) Getty Images/Alex Wong President Barack Obama, accompanied by first lady Michelle Obama and daughters, Sasha Obama and Malia Obama, is sworn in by Chief Justice John Roberts on the West Front of the Capitol in Washington, Monday, Jan. 21, 2013, at the ceremonial swearing-in ceremony during the 57th Presidential Inauguration. (AP Photo/Rob Carr, Pool) Rob Carr President Barack Obama takes the oath of office from Chief Justice John Roberts at the ceremonial swearing-in on the West Front of the U.S. Capitol during the 57th Presidential Inauguration in Washington, Monday, Jan. 21, 2013. (AP Photo/Saul Loeb) AP/Saul Loeb U.S President Barack Obama gives his inaugural address during his inauguration as the 44th President of the United States of America on the West Front of the Capitol Jan. 20, 2009 in Washington, DC. Obama becomes the first African-American to be elected to the office of President in the history of the United States. (Photo by Win McNamee/Getty Images) Getty Images/Win McNamee Crowds gather along the National Mall during the swearing-in ceremony of President-elect Barack Obama, Tuesday, Jan, 20, 2009, in Washington. (AP Photo/Luis M. Alvarez) ASSOCIATED PRESS/Luis Alvarez A crowd on the National Mall listen to the inaugural address of President Barack Obama at the U.S. Capitol in Washington, Tuesday, Jan. 20, 2009. (AP Photo/Susan Walsh) AP/Susan Walsh U.S. President George W. Bush takes the oath of office from U.S. Supreme Court Chief Justice William Rehnquist (L) during inaugural ceremonies with (L to R) first lady Laura Bush and daughters Barbara Bush and Jenna Bush looking on at the west front of the U.S. Capitol Jan. 20, 2005 in Washington, D.C. Bush was sworn in for a second term. (Photo by Shaun Heasley/Getty Images) Getty Images/Shaun Heasley U.S. President George W. Bush delivers his inaugural address after taking the oath of office for his second term during ceremonies on the west front of the U.S. Capitol Jan. 20, 2005 in Washington, D.C. Bush?s address outlined his plans to pursue freedom around the world and push a legacy-setting agenda at home championing ?freedom in all the world? as the surest path to peace. (Photo by Shaun Heasley/Getty Images) Getty Images/Shaun Heasley President Bush and Vice President Cheney leave the stage following the conclusion of the Inauguration ceremonies at the United States Capitol in Washington, Tuesday, Jan. 20, 2005. (AP Photo/Susan Walsh) AP/SUSAN WALSH Newly sworn in President George W. Bush gives his inaugural address Jan. 20, 2001 outside the US Capitol overlooking the National Mall in Washington. (Photo by Joe Raedle/Newsmakers) Getty Images/Joe Raedle President Clinton gives his inaugural speech after being sworn in for his second term by Supreme Court Chief Justice William Rehnquist during the 53rd Presidential Inauguration Monday, Jan. 20, 1997, in Washington. (AP Photo/Wilfredo Lee) AP/WILFREDO LEE In this file photo from Oct. 16, 1995, the view from the Washington Monument toward the Capitol shows the participants in the Million Man March in Washington. Federal. (AP Photo/Steve Helber, File) ASSOCIATED PRESS/Steve Helber With the Washington Monument in the background, participants in the Million Man March gather on Capitol Hill and the Mall in Washington Monday Oct. 16, 1995. Tens of thousands of black men from across America gathered at the base of the Capitol, and the Mall, in a rally of unity, self-affirmation and protest. (AP Photo/Mark Wilson) ASSOCIATED PRESS/MARK WILSON Thousands gather on the Mall Sunday to listen to a concert in front of the Lincoln Memorial and to see President-elect Clinton at the beginning of a five-day inaugural celebration culminating with Clinton’s inauguration Wednesday Jan. 17, 1993. The day, which began for Clinton in the Thomas Jefferson’s home of Monticello, concluded with fireworks over the Potomac. (AP Photo/Stephan Savoia) ASSOCIATED PRESS/STEPHAN SAVOIA This Jan. 20, 1981 file photo shows a wide angle view from the Capitol balcony as President Ronald Reagan, visible at center, addresses the nation following his swearing-in ceremony in Washington. (AP Photo, File) ASSOCIATED PRESS A huge crowd jams the mall in Washington on Sunday, July 4 1976, the nation’s 200th birthday-during the People’s Bicentennial Commission’s demonstration. In background is the Washington Monument. (AP Photo) AP Shown in photo is a General view of Moratorium Day in Washington on Oct. 15, 1969. (AP Photo) ASSOCIATED PRESS ( 1 /20) Share This Gallery: Share on Facebook. Share on Twitter. Share via email. Print.

WASHINGTON — President Donald Trump promised “massive crowds” for his inauguration Friday. Did they show up?

It’s still too early for any official estimates of the number of inauguration revelers. Visitors reported large crowds on the National Mall, although aerial photos showed far fewer people than the enormous number of attendees for President Barack Obama’s first inauguration in 2009.

Before the inauguration, officials said they were expecting between 800,000 and 900,000 people in D.C.

One indicator of crowd size — although it doesn’t tell the whole story — is the number of trips taken on D.C.’s Metro system.

As of 11 a.m. on Inauguration Day, Metro said it had recorded 193,000 trips. That’s about on par with the number of trips taken for President George W. Bush’s second inauguration in 2005. In 2013 during Obama’s second inauguration, the system had recorded about 317,000 trips. During Obama’s record-setting 2009 inauguration, the system had recorded 513,000 Metro trips by 11 a.m.

Obama’s first inauguration in 2009 still holds the record for the highest attended presidential inauguration — 1.8 million packed the National Mall, the Capitol Grounds and crammed D.C. streets.

That bested Lyndon Johnson’s previous record of 1.2 million people for his 1965 inaugural.

Estimating large crowds is a notoriously tricky business, however. In fact, the National Park Service 20 years ago stopped estimating crowd sizes after a dispute about its estimate of the number of people at the 1995 Million Man March led to the threat of a lawsuit. (The agency said 400,000 people showed up, but Metro trips recorded that day far surpassed that number and an independent analysis indicated the number of participants may have been twice as high.)

The estimate for the record-shattering crowds for Obama’s 2009 inauguration came from the D.C. mayor’s office and a slew of local and federal agencies responsible for managing traffic and security for the event, and the park service did not dispute it.

Presidential inaugurations aren’t the only big events to draw crowds to the mall. Protests and holiday celebrations have also drawn throngs.

The largest demonstration in D.C. (back when the National Park Service was still keeping head counts) came in November 1969 when a crowd of between 600,000 anti-war protesters gathered on the National Mall.

A fireworks display on the National Mall in 1976 to mark the U.S. Bicentennial was estimated to have drawn about 1 million celebrants.

Scroll through the gallery above to get a bird’s-eye view of crowds on the National Mall. Another view of inaugurations through the years is below.