This special issue of the Johns Hopkins APL Technical Digest celebrates APL's 75th anniversary. It includes historic highlights of the mission areas in APL's four current sectors, as well as articles on the Lab's research and analysis organizations. Additional articles capture important elements of APL's history and culture: its tradition of offering diverse educational opportunities to its staff, highlights from our longstanding Colloquium series, the history of the Technical Digest itself, the Lab's commitment to awarding staff members' achievements, APL's ever-evolving facilities and capabilities, and our previous directors.