In 1944, upon the death of her husband, Richard, and with the ranch lands held in trust, Marguerite “Daisy” O’Neill stepped forward to lead the family. With determination and pride, she kept the ranch land intact. To this day, Marguerite O’Neill’s admonition to “take care of the land and the land will take care of you” guides the family, and the community.
In the early 1960's, urbanization had reached the borders of The Ranch. In response to Orange County’s quickly growing need for housing, the O’Neill family and its partners created the 10,000-acre planned community of Mission Viejo. Since that time, they’ve continued to create places to live while remaining committed to preserving Rancho Mission Viejo through their dedications of ranch land, such as O'Neill Regional Park, Riley Wilderness Park, Ronald W. Caspers Wilderness Park, and The Reserve at Rancho Mission Viejo.
In 2005, the O’Neill family secured a science-based land use and open space preservation plan for the remaining 20,868 acres of family ranch. Under this plan, about 25% of The Ranch will be carefully planned over the next few decades into a new community, while the remaining 75% will be forever protected as The Reserve at Rancho Mission Viejo.