Ten years ago today, September 11, 2001 began as an ordinary Tuesday and ended as a day none of us would forget.

Nearly 3,000 people were killed. The World Trade Center towers were destroyed, the Pentagon was attacked, and Flight 93 crashed in Pennsylvania. Many of us can still remember exactly where we were when we first realized what was happening.

A lot has changed in the ten years since.

Air travel is different. Security lines, identification checks, removing shoes and restrictions on what we can carry have become routine. The Transportation Security Administration and Department of Homeland Security were both created after the attacks, and increased security has become part of everyday life in ways that would have seemed unusual before September 11.

The country has also spent most of the last decade at war. American forces entered Afghanistan shortly after the attacks, targeting al-Qaeda and the Taliban government that had provided it sanctuary. Two years later the United States invaded Iraq. Thousands of American service members have been killed and many more wounded.

Earlier this year, Osama bin Laden was killed in Pakistan. His death does not undo anything that happened ten years ago, but it was a moment many people wondered if they would ever see.

There have also been difficult debates about how much privacy and freedom we are willing to exchange for security. Laws such as the Patriot Act changed the government’s ability to investigate terrorism, and those questions are still being debated today.

But September 11 should not only be remembered for wars, laws, airports or government agencies.

It should be remembered for the people.

The people who went to work that morning. The passengers and crews who boarded four airplanes. The firefighters, police officers and first responders who ran toward danger. The passengers of Flight 93 who decided to fight back. And the families who have spent the last ten years without someone they loved.

Today, the National September 11 Memorial is being dedicated at the World Trade Center site. Its two reflecting pools sit within the footprints of the Twin Towers, surrounded by the names of those who were killed.

A lot has changed in ten years.

The reason we remember September 11 has not.

Nearly 3,000 people began an ordinary day and never came home.

Today is a day to remember them.