US to commemorate 9/11 as its aftermath extends and evolves

FILE- In this May 15, 2015 file photo, visitors gather near the pools at the 9/11 Memorial in New York. As they have done 17 times before, a crowd of ...
FILE- In this Sept. 9, 2015 file photo, visitors look at the waterfalls at the World Trade Center Memorial in New York. As they have done 17 times bef...
Kiersten Haub, from left, Erika Starke, and Michael Haub, family members of New York firefighter Michael Haub, attend a second funeral service for him...
A visitor to the Flight 93 National Memorial in Shanksville, Pa., views the Wall of Names on Tuesday, Sept. 10, 2019, as the nation prepares to mark t...
Visitors to the Flight 93 National Memorial in Shanksville, Pa., participate in a sunset memorial service on Tuesday, Sept. 10, 2019, as the nation pr...
New York Fire Department members attend a second funeral service for FDNY firefighter Michael Haub in Franklin Square, N.Y., Tuesday, Sept. 10, 2019. ...
Visitors to the Flight 93 National Memorial in Shanksville, Pa., participate in a sunset memorial service on Tuesday, Sept. 10, 2019, as the nation pr...
New York Fire Department members attend a second funeral service for FDNY firefighter Michael Haub in Franklin Square, N.Y., Tuesday, Sept. 10, 2019. ...
Norma Molina, of San Antonio, Texas, leaves flowers by the names of firefighters from Engine 33 at the September 11 Memorial, Monday, Sept. 9, 2019, i...
FILE - In this Sept. 11, 2001, file photo, smoke rises from the burning twin towers of the World Trade Center after hijacked planes crashed into the t...
FILE - In this Sept. 11, 2001, file photo, firefighters work beneath the destroyed mullions, the vertical struts that once faced the outer walls of th...

FILE- In this May 15, 2015 file photo, visitors gather near the pools at the 9/11 Memorial in New York. As they have done 17 times before, a crowd of ...

FILE- In this Sept. 9, 2015 file photo, visitors look at the waterfalls at the World Trade Center Memorial in New York. As they have done 17 times bef...

Kiersten Haub, from left, Erika Starke, and Michael Haub, family members of New York firefighter Michael Haub, attend a second funeral service for him...

A visitor to the Flight 93 National Memorial in Shanksville, Pa., views the Wall of Names on Tuesday, Sept. 10, 2019, as the nation prepares to mark t...

Visitors to the Flight 93 National Memorial in Shanksville, Pa., participate in a sunset memorial service on Tuesday, Sept. 10, 2019, as the nation pr...

New York Fire Department members attend a second funeral service for FDNY firefighter Michael Haub in Franklin Square, N.Y., Tuesday, Sept. 10, 2019. ...

Visitors to the Flight 93 National Memorial in Shanksville, Pa., participate in a sunset memorial service on Tuesday, Sept. 10, 2019, as the nation pr...

New York Fire Department members attend a second funeral service for FDNY firefighter Michael Haub in Franklin Square, N.Y., Tuesday, Sept. 10, 2019. ...

Norma Molina, of San Antonio, Texas, leaves flowers by the names of firefighters from Engine 33 at the September 11 Memorial, Monday, Sept. 9, 2019, i...

FILE - In this Sept. 11, 2001, file photo, smoke rises from the burning twin towers of the World Trade Center after hijacked planes crashed into the t...

FILE - In this Sept. 11, 2001, file photo, firefighters work beneath the destroyed mullions, the vertical struts that once faced the outer walls of th...

NEW YORK (AP) — Americans are commemorating 9/11 with mournful ceremonies, volunteering, appeals to "never forget" and rising attention to the terror attacks' extended toll on responders.

A crowd of victims' relatives is expected at ground zero Wednesday. President Donald Trump is scheduled to join an observance at the Pentagon.

Vice President Mike Pence is to speak at the third attack site, near Shanksville, Pennsylvania.

Eighteen years after the deadliest terror attack on American soil, the nation is still grappling with the aftermath at ground zero, in Congress and beyond.

The attacks' aftermath is visible from airport security checkpoints to Afghanistan, where a post-9/11 invasion has become America's longest war.

Nearly 3,000 people were killed when hijacked planes rammed into the World Trade Center, the Pentagon and a Shanksville field on Sept. 11, 2001.