Freeway Park does not try to pretend it is a meadow. Its design is unabashedly brutalist: massive geometric concrete walls rise and angle overhead, channeling visitors through narrow passages that suddenly open into sunlit plazas. Waterfalls cascade down stacked concrete forms, their sound engineered to mask the traffic drone below. Danadjieva, a Bulgarian-born architect who had studied the canyons of the American Southwest, modeled the park's spaces on those geological forms, creating what she called an urban canyon experience. Lush plantings of ivy, ferns, and evergreen shrubs soften the raw concrete, so the overall effect is less fortress and more grotto. An expansion in 1982 extended the park several blocks up First Hill, adding a stairway and wheelchair ramp that connected downtown commuters to one of Seattle's oldest residential neighborhoods.

When Interstate 5 sliced through Seattle in the early 1960s, it created a physical and psychological chasm between downtown and the First Hill neighborhood to the east. The freeway trench was loud, ugly, and impassable on foot. Civic leader Jim Ellis, who had already championed the regional transit system and the cleanup of Lake Washington, saw the potential to bridge that gap. The idea of lidding a freeway was radical at the time. No American city had attempted anything like it. Halprin, already famous for the Lovejoy and Ira Keller fountains in Portland, was hired to make it real. The resulting park did not merely cover the highway; it created a genuine pedestrian connection between the convention center, downtown offices, and First Hill residences, a piece of infrastructure disguised as a garden.

For all its design ambition, Freeway Park's secluded alcoves and dense plantings created blind spots that attracted crime. A murder on January 18, 2002, crystallized fears and led to calls for a radical redesign or even demolition. The Freeway Park Neighborhood Association formed in response, collaborating with the city's parks department on an activation plan published in 2005 as "A New Vision for Freeway Park." The group's conclusion was counterintuitive: the park's problems were not primarily architectural but social. Better lighting, pruned sightlines, increased security patrols, and most importantly more foot traffic from organized events and convention center visitors could reclaim the space. The strategy worked. By the late 2000s, crime in the park had dropped 90 percent compared to its 2002 peak. In 2008, the park was renovated and formally renamed to honor Jim Ellis.

On October 25, 2019, the Washington Heritage Register voted unanimously to list Freeway Park, and on December 19 of that year, the park was added to the National Register of Historic Places. The recognition cemented its status as more than a local curiosity. Freeway Park is now studied as a precedent by urban planners worldwide, from the Klyde Warren Park deck in Dallas to the proposed cap parks over highways in dozens of other American cities. The original brutalist fountains, with their stark geometries and thundering water, remain the park's signature feature, drawing architecture students and parkour enthusiasts alike. On a clear day, the park's upper terraces offer glimpses of Elliott Bay to the west and the slopes of First Hill to the east, a reminder that this garden exists precisely because someone decided a highway did not have to be the last word.