Incidence of Acute Kidney Injury (AKI) has increased dramatically over the past two decades due to rising prevalence of comorbidities and broadening repertoire of nephrotoxic medications. Hospitalized patients with AKI are at higher risk for complications and mortality, thus early recognition of AKI is crucial. Building AKI prediction models based on electronic medical records (EMRs) can enable early recognition of high-risk patients, facilitate prevention of iatrogenically induced AKI events, and improve patient outcomes. This study builds machine learning models to predict hospital-acquired AKI over different time horizons using EMR data. The study objectives are to assess (1) whether early AKI prediction is possible; (2) whether information prior to admission improves prediction; (3) what type of risk factors affect AKI prediction the most. Evaluation results showed a good cross-validated AUC of 0.765 for predicting AKI events 1-day prior and adding data prior to admission did not improve model performance.