Many congenital conditions and surgical interventions perturb the hemodynamics experienced by proximal pulmonary arteries during early postnatal development, thus leading to differential gene expression and associated changes in vascular structure and function. Among these, pathologic conditions include patent ductus arteriosus, pulmonary atresia and stenosis, and hypoxemia-induced pulmonary hypertension while surgical interventions include the placement of a Blalock-Taussig shunt as well as Glenn, Fontan, and Norwood procedures. Despite the significant morbidity associated with these diverse conditions, there has been little attention directed towards understanding natural postnatal development of pulmonary arteries from both biological and mechanical perspectives. Without such information, we cannot truly understand the phenotype of the affected pulmonary artery, which is fundamental to improving diagnosis, treatment, and prognosis. In this paper, we present novel data from wild-type mice that document normal postnatal changes in select gene expression, vascular wall composition, and biomechanical properties of proximal pulmonary arteries. These findings enabled the establishment of a novel, data-informed computational model of pulmonary artery development capable of simulating outcomes in response to perturbations in the pulmonary artery hemodynamic environment.