Hurricane Rita, a massive storm packing 165-mph winds and destructive force equal to the might of Hurricane Katrina, tracked through the Gulf of Mexico on Wednesday, prompting evacuation orders for more than 1.1 million Texans and the few remaining holdouts in storm-ravaged New Orleans.

After nicking the Florida Keys as a Category 2 storm, Rita intensified to Category 5 status, the highest ranking used by the National Hurricane Center. Authorities in Galveston, Tex., a coastal city of 60,000, ordered mandatory evacuations.

By midday, a 20-mile line of cars snaked up Interstate 45 out of Galveston -- scene of the deadliest hurricane in U.S. history when an unnamed storm killed 8,000 to 10,000 people in 1900. Thousands of cars crammed roads around Houston, the nation's fourth-largest city, where authorities also ordered residents in low-lying areas to evacuate.

About 1,000 state troopers were staged near the Gulf Coast, while dozens of shelters prepared for evacuees in Austin, Lufkin, College Station-Bryan, San Antonio and Huntsville. In Austin, which just three weeks ago took in 4,000 Katrina evacuees, 50 shelters were being opened to house as many as 15,000 Texas Gulf Coast evacuees.

President Bush declared states of emergency in Texas and Louisiana. Texas Gov. Rick Perry (R) urged residents along a 250-mile swath, from Beaumont to Corpus Christi, to leave.

"I urge the citizens to listen carefully to the instructions provided by state and local authorities, and follow them," Bush said during a speech in Washington. "We hope and pray that Hurricane Rita will not be a devastating storm, but we've got to be ready for the worst."

In recent days, Rita has grown into a giant storm with hurricane-force winds stretching 45 miles from its center and tropical storm force winds extending 140 miles. Forecasters project Rita will make landfall early Saturday along the central Texas coast. However, even a slight shift north would put New Orleans back in the bull's-eye, prompting fears the city's already-fragile levee system could be breached again, flooding neighborhoods that remain coated in a crusty layer of muck.

Painful memories of Katrina -- with a death toll that reached 1,000 Wednesday -- drove thousands of private citizens and elected officials to act fast rather than take the wait-and-see approach that greeted some coastal storms in recent years.

"If Katrina did anything, it woke people up to the power of Mother Nature," said Anthony Griffin, 51, who spent Wednesday boarding up his Galveston law office before heading to his brother's home in Fort Worth. "When Katrina hit this country, it was in a city that everyone knew and those folks looking at the TV camera looked like folks we knew."

In Texas, Perry urged those in the path of the storm to evacuate. "Homes can be rebuilt; lives cannot," he said from the governor's mansion in Austin. "If you're on the coast between Beaumont and Corpus Christi, now's the time to leave."

The Department of Defense, taking lessons from Katrina, intends to send surveillance aircraft soon after Rita strikes land to "determine the magnitude of the relief required and, secondly, where it would be required," said Paul McHale, assistant secretary of defense for homeland defense. "We want to ensure as a matter of policy we have better eyes on target."

Already, about 5,000 Texas National Guard troops have been mobilized and another 1,300 who had been assisting in New Orleans are returning from Louisiana. The Pentagon is drawing up plans to assist local law enforcement "in the event that the first responders become the first victims," as happened in Katrina, he said. "The National Guard MP [military police] response to Katrina was nothing short of extraordinary, but it was a response that was formulated on the fly as we recognized an emerging law enforcement requirement," he said.

The Federal Emergency Management Agency positioned 45 truckloads of water and ice and 25 truckloads of Meals Ready to Eat at Fort Sam Houston in San Antonio. More than 400 medical workers and 14 urban search-and-rescue teams, comprising 744 people, have been stationed in Houston, San Antonio and Fort Worth.

"The most important thing that we're doing is work with the Department of Defense to use their assets up front before the storm instead of waiting until after the storm lands," said acting FEMA Director R. David Paulison. Earlier this week, a military satellite communications system was shipped to New Orleans.

FEMA also asked the Pentagon to provide 26 helicopters to ferry people and supplies, five two-person communications teams for first responders, temporary hospital beds for 2,500 patients and field kitchens capable of serving 500,000 meals a day.

The Centers for Disease Control and Prevention in Atlanta assembled four teams of 20 to deploy after Rita makes landfall, Tom Skinner, an agency spokesman, said. The CDC has three dozen staffers in Texas as part of its Katrina recovery effort, providing care at shelters, hospitals and local health departments.

After suffering sizable losses in Katrina, several oil refineries shut down Wednesday, pulling hundreds of workers from rigs off the Texas shore. The Texas area accounts for about one-quarter of the nation's total crude oil production.

In New Orleans, pockets of rescue workers and cleanup crews kept watch on the weather map even as they struggled to restore critical services in a metropolitan area that just one month ago bustled with 1.3 million residents and thousands of revenue-generating tourists. A team of seven Public Health Service doctors and nurses planned to stay in New Orleans through Rita, but about 45 CDC employees relocated to Baton Rouge.

Louisiana state officials were moving about 75 homebound patients from "special needs" shelters in Lafayette and Thibodaux to centers in Monroe and Shreveport, said Bob Johannessen, spokesman for the state Department of Health and Hospitals.

Still, even going more than weeks without power, water or sewer service were not enough to uproot some here. After surviving the Mariel boatlift from Cuba in 1980 and Katrina on Aug. 29, Jose Mendez, 66, said he was not frightened by Rita.

Speaking in Spanish in his mildewed apartment near the New Orleans Fairgrounds horse-racing track, Mendez smiled: "I know how to deal with water."

Moreno reported from Austin. Staff writers Manuel Roig-Franzia in New Orleans, Blaine Harden in Houston and Christopher Lee, Spencer S. Hsu and Ann Scott Tyson in Washington also contributed to this report.

Galveston, Tex., schools police officer Mary Fullen, center, helps an evacuee family at the Island Community Center ahead of Hurricane Rita. Driver Coleman Mack counts residents aboard his bus in Galveston to evacuate to Huntsville, Tex. Thousands of vehicles leave Houston on U.S. Highway 59 to escape Hurricane Rita.