Two years ago, as she was browsing through the historic New England home of Frederick Law Olmsted, the father of landscape architecture in the United States, Gail Spilsbury accidentally stumbled upon an artifact that would change the direction of her life.

The Washington-based author had spotted Olmsted’s son’s little-known 1918 Rock Creek Park report. Taken out of storage for a special event that day, the small, square book that was intended to guide the park’s development and maintenance inspired Spilsbury to write her recently published book, the aptly named “Rock Creek Park.”

“I didn’t know what my book was going to be about,” Spilsbury said, “but I wanted Washingtonians to know” about the Olmsteds’ contribution to their city and Rock Creek Park in particular. “The Olmsteds should be remembered,” she said.

Within a week of her return from the national historic site in Brookline, Mass., the 50-year-old author had obtained a copy of the Olmsted report from the Library of Congress. After delving further into the park’s history, she quickly found out that the story was much larger than the 1918 report.

Using research skills that were finely tuned while working toward her bachelor’s and master’s degrees in history from the University of California at Berkeley, the small, trim woman learned of the McMillan Plan of 1902. Named after Sen. James McMillan (R-Mich.), who chaired the Committee on the District of Columbia, the report “served for decades as the blueprint for Washington’s development, and it continues to exert influence today,” Spilsbury says in her book. Frederick Law Olmsted Jr., who later wrote the 1918 Rock Creek Park report, was an influential member of McMillan’s commission and helped draft the final plan.

Seven years after the plan was written, Spilsbury writes, the Olmsted brothers’ firm “was contracted to study Rock Creek Park, resulting in the Report of 1918.” In an excerpt from the report, reprinted in Spilsbury’s book, Olmsted Jr. warned that “The dominant consideration, never to be subordinated to any other purpose in dealing with Rock Creek Park, is the permanent preservation of its wonderful natural beauty, and the making of that beauty accessible to the people without spoiling the scenery in the process.”

Spilsbury said that Olmsted Jr., the youngest member of the group that redesigned Washington, lived much longer than his team members. He “lasted until 1957 to make sure the plan was implemented,” the author said.

“He helped as Washington evolved to make the right shifts,” she said.

With only three major park “intrusions” since Olmsted Jr.’s time — the golf course, the tennis court complex and the Carter Barron Amphitheatre — Spilsbury commended the National Park Service for keeping the park’s 1,754 acres “as natural as possible” and said Olmsted Jr. would be “relatively pleased” about the park’s condition today, given Washington’s intense urban environment.

The Olmsteds also left their mark on Capitol Hill. The elder Olmsted designed much of the Capitol grounds’ landscaping and the West Front terraces in the 1870s. The father of American landscape design is most famous for his designs for Central Park in New York City and the parks of Boston’s Emerald Necklace.

Aside from her goals of sharing the Olmsted report with other Washingtonians and paying tribute to the family who significantly contributed to America’s landscape culture, the Tenleytown resident also hoped to “encourage continued preservation and appreciation of this great city and natural treasure.”

Toward that end, the last four sections of the 96-page volume detail Rock Creek Park’s chronology, vegetation, bridges and current activity offerings.

While writing the book, Spilsbury routinely rose at 4 a.m. to get a few hours of work in before heading to her day job as an editor at the Smithsonian’s Freer and Sackler galleries. After a year spent also working nights and weekends on the tome, the author took a month-long leave of absence in March to collect the striking photos and drawings that bring the story to life.

“It was tough,” Spilsbury said. “I said I’d never work those hours again, and I’m not doing it again.”

In July, Spilsbury left her post at the Smithsonian to write a new book spawned by “Rock Creek Park.” For the book, titled “The Washington Sketchbook,” Spilsbury is researching and writing about 48 watercolor paintings and pen-and-ink drawings done by R.L. Dickinson in 1918. She found the images in the Library of Congress while searching for Rock Creek Park artwork. She hopes to finish researching and start writing in December.

The second of five children, Spilsbury said she has wanted to be a writer since fourth grade. She married a Foreign Service officer in 1981 and lived for six years in Italy, four years in Poland and two years in Guyana. During that time she wrote newspaper and magazine articles in addition to teaching English.

“I miss traveling and living in foreign cultures,” she said of her time overseas. “I hope to do it again.”

These days, the author said she likes to spend her free time hiking and biking in the park. Although she decried the absence of a bike path all the way through, she said the park is in good shape.

She said she hopes her book “increases public and city awareness of the park to generate greater public activism in support of its longevity.”