Send to the MercyOne Medical Records department by fax at 712-279-2207, or by mail at: Attn: Medical Records. MercyOne Siouxland Medical Center. 801 5th Street. Sioux City, IA 51101. With questions, please call the MercyOne at 712-279-2081 from 8 a.m. to 4:30 p.m..