21st Century Conservation Service Corps Act of 2017 This bill amends the Public Lands Corps Act of 1993 to replace provisions that established the Public Lands Corps with provisions establishing the 21st Century Conservation Service Corps (21CSC) to: engage youth and veterans in civilian national service positions to conserve, rebuild, and enhance the natural resources, infrastructure, and recreation assets of the United States; increase public access to, and use of, public and tribal land and water, infrastructure, and natural, cultural, and historical resources, while spurring economic development and outdoor recreation and addressing backlogged maintenance on public land; conserve, restore, and enhance such resources by carrying out high-quality, cost-effective projects; ensure that the activities and expertise of corpsmembers will be accessible to any public, nonprofit, or tribal entity responsible for the stewardship of land and water in coordination with the land or water owner; place youth and veterans in civilian national service positions to protect, restore, and enhance U.S. natural resources, infrastructure, and recreation assets in a cost-effective manner without undue duplication or overlap of federal agency activities or programs; and channel widespread interest among youth and veterans in serving in such positions to help conserve, restore, and enhance public and tribal land and water, infrastructure, and natural, cultural, and historical resources and to develop the next generation of outdoor stewards, entrepreneurs, recreationists, and sportsmen. The 21CSC shall be implemented jointly by the participating entities, which shall include the Corporation for National and Community Service, the Office of the Assistant Secretary of the Army for Civil Works, the Federal Emergency Management Agency, and the Departments of Interior, Agriculture, Transportation, Labor, Energy, Defense, Veterans Affairs, Commerce, Education, and Housing and Urban Development. Such entities shall: (1) establish a process for an organization to become a 21CSC organization, and (2) support 21CSC projects. A 21CSC organization shall provide to each youth or veteran corpsmember a wage, stipend, living allowance, and/or an educational credit, as well as skills development, credentials, and education, for participation in a 21CSC project that involves: specified conservation and restoration projects; the support, development, and enhancement of outdoor recreation or urban green space; service that is primarily indoors with a clear benefit for natural, cultural, or historic resources or treasures; or a project on private land or water having a direct or recognized public or environmental benefit or the funding of which originated from a governmental entity. The bill sets forth provisions governing 21CSC conservation centers and program support, the provision of resource assistants, and Corpsmember eligibility for a noncompetitive hiring status and national service educational awards. A participating entity may offer to enter into a cooperative agreement with a tribal agency or a 21CSC organization to establish and administer the Indian Youth 21st Century Conservation Service Corps, which shall carry out 21CSC projects on tribal land or water.