"A crimson cross of St. Andrew on a field of white" is the official description of Alabama's state flag (patterned after the Confederate battle flag). The Alabama legislation does not specify whether the flag should be square or rectangular (only that the bars be at least 6 inches broad), and it is seen both ways.

The original flag of the "Republic of Alabama" (approved by the Alabama Secession Convention in 1861) was very different. Designed by a group of Montgomery Alabama women, it featured the Goddess of Liberty and the words "Independent Now and Forever" on one side - Secession Convention Flag Side 1. The other side displayed a cotton plant and a coiled rattlesnake with the Latin words, "NOLI ME TANGERE" (Touch Me Not) - Secession Convention Flag Side 2. This flag was removed after only one month due to damage by severe weather, and was never flown again.

From 1861 to 1865, a Confederate National flag was flown in Alabama. After the end of the Civil War, the United States flag was flown at official occasions until 1895, when the present Alabama State Flag was authorized.

Source:

Official symbols & emblems of Alabama : AL Archives

Links:

St. Andrew and his Cross: Scottish History Online
Confederate National Flag: Civil War @ Smithsonian
Civil War Flags: National Park Service KidzPage
6th Alabama Infantry Regimental photo album: RootsWeb
State Flags - 50 states List
National Flag