Nestled in the heart of the Historic District, this extraordinary 1929 cottage presents a once-in-a-generation opportunity to own a true landmark of San Juan Capistrano. Designed by Acjachemen tribal leader, Clarence Lobo, this Mills Act-registered residence offers the potential for substantial property tax savings while preserving a chapter of local history. Known as the Father O'Sullivan House, the home is deeply connected to one of San Juan Capistrano's most beloved historical figures. Father St. John O'Sullivan, who personally spearheaded the restoration of the Historic Mission beginning in 1910, once called this property home. Rich in heritage and architectural significance, the residence has been thoughtfully updated to honor its historic character while providing comfort and convenience. Oak wood flooring, authentic architectural details, and abundant natural light create a warm and timeless atmosphere throughout. The beautifully remodeled galley kitchen features premium quartzite countertops, a deep wash-style sink and an abundance of sleek flat-panel cabinetry. Adjacent to the kitchen, a highly functional mudroom discreetly houses the laundry area, refrigerator and has additional storage, preserving the kitchen's clean aesthetic while maximizing utility. The primary suite opens directly to the backyard and its own romantic porch, creating a peaceful retreat overlooking the expansive yard. The guest bedroom is ideally positioned at the front of the home, offering privacy & separation from the primary suite. An exceptional and highly uncommon feature is 'La Casita', a detached studio-style guest cottage that adds tremendous versatility and value. Complete with vaulted ceilings, a kitchenette, updated bathroom & private entrance, this charming living space meets the needs of many. Outside, the generous flat lot has been thoughtfully landscaped with native plantings that provide year-round color, texture and beauty. From the front yard, enjoy views of the Mission Basilica and the surrounding historic landscape. The home is located approximately one-half mile from the iconic Mission San Juan Capistrano, founded in 1776, and offers exceptional walkability to downtown SJC. The area continues to benefit from major public & private investment, including city-led revitalization projects & business renovations inspired by the success of River Street Marketplace, just a five-minute walk away. Properties of this historical significance rarely become available.