The treatment, genotyping and phenotyping of patients with WHO Group 1 pulmonary arterial hypertension (PAH) has evolved dramatically in the last decade.The USPHSR was established as the first US PAH patient registry to investigate genetic information, reproductive histories, and environmental exposure data in a contemporary patient population.and Methods: Investigators at 15 US centers enrolled consecutively screened adults diagnosed with Group 1 PAH who had enrolled in the National Biological Sample and Data Repository for PAH (PAH Biobank) within 5 years of a cardiac catheterization demonstrating qualifying hemodynamic criteria. Exposure and reproductive histories were collected using a structured interview and questionnaire. The PAH Biobank provided genetic data.Between 2015 and 2018, 499 of 979 eligible patients with clinical diagnoses of idiopathic (IPAH) or familial PAH (N=240, 48%), associated PAH (APAH, N=256, 51%), or pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis (N=3, 1%) enrolled. The mean age was 55.8 years, average BMI 29.2 kg/m2, and 79% were women. Mean duration between symptom onset and diagnostic catheterization was 1.9 years. Sixty-six percent of patients were treated with more than one PAH medication at enrollment. Past use of prescription weight loss drugs (16%), recreational drugs (27%), and oral contraceptives (77%) was common. Women often reported miscarriage (37%); although PAH was rarely diagnosed within 6 months of pregnancy (1.9%). Genetic testing identified pathogenic or suspected pathogenic variants in 13% of patients, reclassifying 18% of IPAH and 5% of APAH patients to heritable PAH (HPAH).Group 1 PAH patients remain predominately middle-aged women diagnosed with IPAH or APAH. Delays in diagnosis of PAH persist. Treatment with combinations of PAH targeted medications are more common than in the past. Women often report pregnancy complications, as well as exposure to anorexigens, oral contraceptives, and/or recreational drugs. Genetic tests frequently identify unsuspected HPAH.