Though a judge sentenced her to 45 days behind bars, Hilton was expected to serve only 23 days because of a state law that requires shorter sentences for good behavior.
Earlier Sunday, Hilton attended the MTV Movie Awards, where she briefly spoke to reporters about her sentence.
Hilton will be housed in the facility's "special needs" unit.
Officers arrested Hilton in Hollywood on Sept. 7. In January, she pleaded no contest to the reckless-driving charge and was sentenced to 36 months' probation, alcohol education and $1,500 in fines.
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