On returning to the United States, Urey received an offer of a National Research Council fellowship to Harvard University, and also received an offer to be a research associate at Johns Hopkins University. He chose the latter. Before taking up the job, he traveled to Seattle, Washington, to visit his mother. On the way, he stopped by Everett, Washington, where he knew Dr. Kate Daum, a colleague from from the University of Montana. Dr. Daum introduced Urey to her sister, Frieda. Urey and Frieda soon became engaged. They were married at her father's house in Lawrence, Kansas, in 1926. The couple had four children: Gertrude Bessie (Elizabeth), born in 1927; Frieda Rebecca, born in 1929; Mary Alice, born in 1934; and John Clayton Urey, born in 1939.