Ivan's center made landfall at about 2 a.m. Central Time near Gulf Shores, Ala., east of New Orleans and west of Florida's panhandle, according to the National Hurricane Center.
At least eight people died in northwest Florida when tornadoes touched down and leveled up to 70 buildings, police said, according to Reuters.
The hurricane the size of Texas weakened to a Category 1 storm as it moved inland but was still expected to dump 15 inches of rain and pack 80 mph winds in some areas, forecasters said. Hundreds of thousands of people were left without power.
Downtown Mobile, Ala., was deserted early Thursday, and downed trees, metal signs, roofing material and other storm debris blocked roads, the Associated Press reported.
"We were wondering at first if we made the right choice or not," said Marc Oliver, who rode out the storm with his family. "We had some trees down in our yard and roofing damage, other than that, we came out pretty good."
"We have never seen a hurricane of this size come into Alabama," Gov. Bob Riley said. He had earlier asked President Bush to declare much of the state a disaster area, a request that was granted, according to the AP.
At 7 a.m. Central Time, Ivan was centered about 90 miles west-southwest of Montgomery, Ala., and was moving north at 17 mph. Forecasters said the storm could move on a northeastern path across much of the South and parts of the Midwest.
Ivan, which had earlier killed at least 68 people in the Caribbean, spared New Orleans a direct hit. The city, which was particularly vulnerable because much of it is below sea level, saw sporadic rain overnight but tropical storm-level winds.
Ivan's waves, which reached 25 feet, destroyed homes along the Florida coast Wednesday. Some 300,000 customers were without power in the four westernmost Florida Panhandle counties. The state was still trying to restore power to about 160,000 hit by hurricanes Charley and Francis weeks earlier.
About 260,000 homes and businesses were without power in Alabama, 36,500 in Louisiana and 70,000 in Mississippi.
-- Compiled from wire reports and other media sources