• Sept. 11
American Airlines Flight 77 slams into the Pentagon’s western facade at 9:37 am.

• By Sept. 23
Ten thousand pounds of collapsed debris is removed to provide access to the damaged area.

• Oct. 18
Demolition, which had been held off to allow for the one-month memorial service, begins. It is expected to take up to eight months.

• Nov. 19
Demolition complete. Reconstruction begins atop the first-floor concrete slab laid in 1941.

• Dec. 23
Around-the-clock work at the site is suspended. All workers are required to take two days off for the holiday. Work then resumes on a six-days-per-week, 20-hours-per-day schedule.

• Dec. 28
First blast window frame is installed.

• Jan. 3
Second- floor deck is nearly completed.

• Feb. 5
The blast windows are installed in on the exterior wall.

• Feb. 25
The first of 3,996 pieces of Indiana limestone are installed.

• March 7
The concrete E Ring exterior wall nears completion.

• April 5
With a final pour on the roof, concrete work is completed.

• May 14
Eighty percent of the limestone facade is completed.

• June 11
The final piece of limestone — a block charred in the original blast and inscribed with the date of the attack — is placed on the exterior. Behind it rests a dedication capsule.

• July
Workers complete the interior of E Ring, installing fixtures, carpet, cable and other finishing touches to prepare for returning occupants.

• Aug. 15
The first group of employees — Navy and Marine Corps personnel — move into the reconstructed E Ring.

• Early September
Workers prepare landscaping around site for Sept. 11 rededication ceremony.