Shocked by the terrorist attack and determined to do something to help its victims, thousands of people flooded hospitals and American Red Cross centers across Maryland yesterday to offer a priceless gift: their blood.

More than 1,000 people showed up at the Baltimore City Red Cross office on Mount Hope Drive by last night, waiting in line, on chairs and on the blue-green carpet. About 1,600 people signed up to give at the Columbia center, filling dozens of sheets of paper with names.

Across the nation, more than 700,000 Americans signed up to give blood within six hours of the first bombing, Red Cross officials said.

Four other Baltimore-area Red Cross centers also were swamped, and area hospitals reassigned staff to accommodate an influx of donors.

"There's nothing concrete you can do at this point besides give blood," said Linda Sprenkle, a schoolteacher who stopped into the Baltimore center on her way home from work. "That's why everybody's here."

"It will be a long night," said Deborah Travers, an official with the Baltimore-Washington region of the Red Cross.

The Red Cross' Baltimore-area centers will open at 8 a.m. today, and staff members are taking calls at 800-448-3543. Linnea Anderson of the central Maryland chapter of the Red Cross urged people to continue giving.

Many people waited hours for their turn to give a pint of blood yesterday, but they said they didn't mind.

"We are a country - we love each other," said June Brown, a mortgage officer from Randallstown, waiting outside the Baltimore center in a long line. "I don't care how long it takes. Nothing is as important as this. We have to think that we're waking up tomorrow and other people aren't."

The woman ahead of her nodded in agreement. "This could be us," said Lisa Jackson, who works in the state's Office of the Public Defender.

Inside, people waited for their name to be called, some glued to television sets giving updates on the destruction in New York and outside Washington. Others talked to seatmates about the incidents.

The Baltimore center wasn't expecting to take donations yesterday, but at least 100 staff and volunteers streamed to the building after the attack and opened at 11 a.m. People were already lined up to give blood.

And, in Baltimore County, hundreds lined up at the Red Cross center south of Bel Air to donate blood.

Outside the tiny Columbia Red Cross center, people sprawled on blankets and lounged in lawn chairs, preparing for an equally long wait. As of 4 p.m., volunteers had helped process about 80 of the approximately 800 people who signed up to give blood.

Brenda George, team manager at the center, said she usually sees about 50 donors a week. Christina Sherman, a student at Howard County Community College, got in about noon and had not lost her resolve four hours later. "I think this is very patriotic here," she said, gesturing to the crowd of people around her. "Everyone's trying to help each other out in some way."

Sun staff writer Kimberly A.C. Wilson contributed to this article.