This report provides background information and potential oversight issues for Congress on the Columbia-class program, a program to design and build a new class of 12 ballistic missile submarines (SSBNs) to replace the Navy's current force of 14 Ohio-class SSBNs. The program was previously known as the Ohio replacement program (ORP) or SSBN(X) program. The Navy has identified the Columbia-class program as the Navy's top priority program. The Navy wants to procure the first Columbia-class boat in FY2021. The Navy's proposed FY2019 budget requests $3,005.3 million in advance procurement (AP) funding and $704.9 million in research and development funding for the program.