A Quiet and Solemn Day of Remembrance 11 and Ground Zero For additional Times coverage of events observing the 11th anniversary of the Sept. 11 terrorist attacks, visit CityRoom. President Obama observed a moment of silence at the White House before heading to the Pentagon, while Vice President Joseph R. Biden Jr. flew to Pennsylvania, where one of four hijacked planes crashed after passengers fought back. Lawmakers planned a ceremony on Capitol Hill and Mitt Romney, the Republican presidential nominee, planned to speak on national security in Nevada. The commemorations 11 years after that grim day were noticeably subdued. New York leaders intentionally kept politicians from speaking at the site of the worst of the attacks to avoid politicizing the moment. While the president and Mr. Romney pulled down advertising for the day in deference to sensibilities, they made no effort to duplicate the show of unity that Mr. Obama and Senator John McCain, then his Republican opponent, staged in 2008 when they appeared together. Instead, Mr. Obama appeared with Michelle Obama, passing through a Marine color guard onto the South Lawn of the White House, where hundreds of staff members waited silently at 8:46 a.m., the time the first plane hit the World Trade Center in 2001. Three bells tolled, the president and first lady bowed their heads, then looked up and put hands over their hearts as a trumpeter played taps. "No matter how many years pass, no matter how many times we come together on this hallowed ground, know this -- that you will never be alone," Mr. Obama told relatives of the slain at the Pentagon. Your loved ones will never be forgotten. They will endure in the hearts of our nation, because through their sacrifice, they helped us make the America we are today -- an America that has emerged even stronger. In Chicago, members of the local fire department observed a moment of silence on the tarmac before Mr. Romney arrived. Mr. Romney had not been scheduled to participate but once he arrived, he went down a line and shook hands with the firefighters and medics. Like Mr. Obama, he made no public remarks but he released a written statement beforehand. "On this most somber day, those who would attack us should know that we are united, one nation under God, in our determination to stop them and to stand tall for peace and freedom at home and across the world," Mr. Romney said, adding his "profound gratitude" to the troops who have gone into battle since the attacks. Other political figures released written statements honoring the fallen and the heroes who tried to save them. While they generally made no reference to the election campaign now under way, some of the statements carried an edge of the policy debate over defense spending and counterterrorism policies. "Our national security must be a priority and we must protect against efforts that would undermine our ability to prevent or respond to another devastating attack," said Representative Eric Cantor of Virginia, the Republican majority leader. The United States should never forget and we must never quit. Ashley Parker contributed reporting from Chicago.