Interlaken Park (called the 'Volunteer Hill Parkway' in the Olmsted Bros. 1903 report) was designed by the Olmsted Brothers in 1908. This park property includes Interlaken Boulevard and is immediately adjacent to Boren Park. It is located in the North Capitol Hill neighborhood at 2451 Delmar Dr E, 98102. It is 51.7 acres.
In the 1903 Olmsted Bros. report, the ‘Volunteer Hill Parkway’ is described as ‘one of the most desirable’ branch parkways that would connect Washington Park with Volunteer Park. Trails already existed in that area as part of the 25-mile bike trail system developed by Assistant City Engineer George Cotterill in the 1890’s, and the roads were planned to follow some of these original paths, traversing and ascending the north slope of Volunteer Hill. The report recommends acquiring enough park property to include the best portions of the wooded ravines and enough of the bluffs to control views east to Lake Washington and the Cascade Mountains. The report also recommended acquiring extra land, especially to the bottom of the steep slopes, to discourage any attempt at development; this would not only provide some protection from landslides but also prevent excessive grading that any private building would require.
The eastern half of the boulevard from Washington Park to 19th Avenue/E Galer St. is a traditional boulevard, a roadway meandering through a residential neighborhood with a wide right-of-way that allows curves in the road and large planting areas. The western half of the boulevard (the Roanoke Extension) continues as a road but is set within a larger, naturalistic park setting. The Olmsted Bros. recommended a curving road that stays close to the crest of the bluff and suggested several rustic bridges over exceedingly steep ravines. The plan also added pedestrian paths that access some of the steeper terrain. There is a pedestrian connection that extends south on a spur to the top of the hill to come within two blocks of Volunteer Park. The report also suggested that the western terminus of the boulevard be extended to the electric car line on Tenth Avenue to provide better access to the park.
The 1909 Commissioner report describes Interlaken Boulevard as being so developed that it need not be discussed. They do, however, describe the ‘West Interlaken Boulevard’ (the Roanoke Extension) as being under construction. The 4100 ft long roadway extended the roadway portion of the boulevard from 19th Avenue and E Galer St. west to Roanoke St and Eleventh Ave N.
An addendum to the Park Commissioners report is a letter from the Olmsted Bros. firm (dated Jan. 5, 1908) that speaks specifically to that Roanoke extension. A major connection of the Boulevard to the west lay along one of the existing bike trails but this trail crossed a property owned by Adelphi College (now the campus of Seattle Prep). The firm evaluated whether the boulevard would inhibit the college from any expansion plans. They determined that several new buildings situated around a central green space could all be built on the plateau at the top of the bluff. The Olmsted Bros. determined that the boulevard was planned to be installed on a slope that was too steep to be used for any large institutional building and that the owners of the property would not be adversely affected by the construction.
In 1913, 5 acres were set aside from Interlake Park and re-named to honor Louisa Boren Denny, a Seattle pioneer. This property encompasses the scenic view point at the top of the bluff at the original pedestrian connection from Interlake Park to Volunteer Park.