Chloe was born in Metropolis in 1987 and moved to Smallville in eighth grade when her father, Gabe, was transferred to LuthorCorp's Plant #3. When she was five, Chloe thought her mother, Moira, abandoned her, but it's later revealed that her mother suffered from a mental illness and was institutionalized when Chloe was twelve. However in season six episode "Progeny", it is revealed that the real reason Moira left was because she was infected by the meteor rocks and has the power to control Chloe and every other infectee and was scared for the safety of her daughter and husband.

According to Clark, when he first met Chloe, the first thing she wanted to know was where she could get a copy of the Daily Planet so she could "keep in touch with civilization." She then insisted on seeing his parents' farm, since she had figured only the Amish were farmers. When Clark showed her his loft, she kissed him on the lips just to "get that out of the way"; it was Clark's first kiss. Chloe remained Clark's platonic friend, though she concealed a deep-seated crush on Clark that sometimes caused her to resent Lana Lang and Clark's seemingly endless infatuation with her.

At the end of the first season, Clark admitted to having some feelings for Chloe, but he was unable to let go of hopes that he might one day be with Lana. Encouraged by parents and friends to go to the dance even if he could not go with Lana, Clark asked Chloe instead. Chloe was delighted, but when a cluster of tornadoes hit Smallville, Clark ran off to find Lana (who was stranded on the edge of town), leaving a crushed Chloe alone on the dance floor.

During the summer between her freshman and sophomore years, Chloe interned at the Daily Planet. She earned this internship without interview after writing about her experiences after being kidnapped and buried alive by a local police officer. The following summer she was given her own column in the Daily Planet after making a deal with Lionel Luthor to dig up information on Clark.

Throughout the series, Chloe has cultivated a close, almost sister-like friendship with Lana Lang (her only female companion besides Lois Lane). She even convinced her father to let Lana stay with them when Lana's aunt moved to Metropolis during their sophomore year. Lana eventually moved into the apartment over the Talon before leaving for college. The fifth season opens with Chloe and Lana as freshmen at Metropolis University. After Chloe's initial roommate throws a tantrum over her "Wall of Weird" she gets freaked out about the vampires in the episode Thirst and transfers to a different university, so Chloe and Lana become roommates once again.

During season five Chloe suffers a nervous breakdown and starts having delusions caused by a vengeful ghost. When examined by a psychiatrist, he determines she is exhibiting signs of hereditary schizophrenia from her mother. When it becomes clear at the end of the episode that the delusions were not caused by Chloe's state of mind, Chloe is so disturbed by the experience that she finally seeks out her mother for the first time in years.

In the season six episode "Freak", it is revealed that Chloe possesses unknown meteor powers, which are later used for the first time in season six finale "Phantom".

Source: wikipedia.org