Lawmakers praised her as a trailblazer and an inspiration for those with disabilities.
The statue shows Keller -- who lost her sight and hearing to illness when she was 19 months old -- standing at a water pump as a 7-year-old, a look of recognition on her face as water streams into her hand.
It depicts the moment in 1887 when teacher Anne Sullivan spelled "W-A-T-E-R" into one of the child's hands as she held the other under the pump.
It's the moment when Keller realized meanings were hidden in the manual alphabet shapes Sullivan had taught her to make with her hands.
"W-A-T-E-R," said Alabama Gov. Bob Riley. "Five simple letters that helped rescue 7-year-old Helen Keller from a world of darkness and a world of silence.
The statue is the Capitol's first to depict a handicapped person and also the first depicting a child.
Keller's statue will replace one depicting Jabez Curry. Curry, who has represented Alabama in the Capitol since 1908, was a Georgia native who served as president of Howard College, which later became Samford University in Birmingham. The Curry statue is being sent back to Alabama for display at the university.