Building No. 105, Boeing Airplane Company, popularly known as "The Red Barn," is historically significant as the birthplace of the Boeing Company and the cradle of the modern American aerospace industry. Originally constructed in 1909 as the Edward Heath Shipyard on the Duwamish River, the two-story, yellow pine timber-frame structure was purchased by timber magnate William E. Boeing in 1910. In 1916, Boeing incorporated the Pacific Aero Products Company (renamed the Boeing Airplane Company in 1917) and utilized this building as his first manufacturing plant, design studio, and corporate headquarters. Featuring a utilitarian design with red-painted cedar siding, this modest workshop was the site where Boeing's earliest aircraft, including the B&W Seaplane and the military-grade Model C, were handcrafted, marking the transition of aviation from a hobbyist's pursuit into a major industrial enterprise.

During World War I, the building served as the production hub for the company's first military contracts, establishing the Pacific Northwest as a cornerstone of the nation's defense and aerospace sectors. After decades of serving various industrial purposes, the historic structure was threatened with demolition in the 1970s. Recognizing its immense historical value, preservationists successfully organized its relocation in 1975, barging the building down the Duwamish River to Boeing Field (King County International Airport). Now meticulously restored as the centerpiece of the Museum of Flight, Building No. 105 is recognized as the oldest surviving aircraft manufacturing plant in the United States and stands as a monumental testament to early 20th-century technological innovation and industrial design.

The Hiram M. Chittenden Locks and Lake Washington Ship Canal, constructed between 1911 and 1916 by the U.S. Army Corps of Engineers, represent a monumental feat of early 20th-century civil engineering. Supervised by and named after Major Hiram M. Chittenden, the district engineer who championed the project, the complex serves as a vital conduit connecting the saltwater of Puget Sound with the freshwater of Lake Union and Lake Washington. The historic district encompasses the large and small locks, a concrete spillway dam with tainter gates, a fish ladder designed to assist migrating salmon, and the surrounding Carl S. English Jr. Botanical Gardens. Officially opened in 1917, the locks remain among the busiest in the United States, embodying a masterful integration of industrial utility, public park planning, and environmental management.

Historically, the canal and locks fundamentally reshaped the geography, hydrology, and economy of the Seattle metropolitan area. By providing a navigable waterway for ocean-going vessels to access protected freshwater harbors, the project catalyzed Seattle's maritime trade, shipbuilding, and timber industries, allowing the city to grow into a premier Pacific port. However, the project also dramatically altered the regional landscape opening the canal lowered the water level of Lake Washington by nearly nine feet, dried up the Black River outlet, diverted the Cedar River, and created miles of new dry shoreline that spurred rapid urban development. Today, the Chittenden Locks and Ship Canal stand as a National Historic Civil Engineering Landmark, illustrating the profound impact of federal water infrastructure on the development of the Pacific Northwest.

The Duwamish No. 1 Site (State Archaeological Site 45-KI-23), listed on the National Register of Historic Places in 1989, is one of the most culturally and archaeologically significant indigenous sites in the Puget Sound basin. Located along the transition zone of the Duwamish River in King County, Washington, this multi-component shell midden and habitation site represents more than a millennium of continuous and seasonal occupation by the Duwamish (Coast Salish) people, with radiocarbon dates indicating use from approximately 600 CE well into the historic period of European contact. As one of the few surviving, intact archaeological resources in a highly industrialized river valley, the site holds immense significance for its potential to yield critical information regarding pre-contact settlement patterns, technological adaptations, and the socio-economic organization of the region's native inhabitants.

Excavations at the site have revealed a rich deposit of cultural material, including dense shell middens, hearths, fire-cracked rock, and a diverse assemblage of bone, antler, and stone tools. These findings document a sophisticated subsistence strategy focused on the intensive harvesting of estuarine resources, particularly salmon, flatfish, and various shellfish species, complemented by the hunting of terrestrial mammals and waterfowl. Beyond its scientific value to Pacific Northwest archaeology, the Duwamish No. 1 Site carries profound historical and spiritual importance for the contemporary Duwamish Tribe, serving as a tangible link to their ancestral homeland, traditional lifeways, and enduring presence in the Seattle metropolitan area.

Built in 1918 on the shores of Seattle's Union Bay, the Naval Military Hangar-commonly known as the University Shell House-stands as a rare surviving example of World War I-era wooden military aviation architecture. Originally constructed by the U.S. Navy to house seaplanes for a naval aviation training camp, the hangar was completed just as the war ended, preventing its use for its intended military purpose. In 1919, the Navy transferred ownership of the massive wood-frame, bowstring-truss structure to the University of Washington, paving the way for its transformation into one of the most storied athletic facilities in American collegiate history.

The building's primary historical significance stems from its association with the University of Washington's legendary rowing program and the master boatbuilder George Pocock, who established his workshop in the building's loft. Within this hangar, Pocock crafted the world-renowned cedar racing shells that revolutionized the sport of rowing. Most famously, the Shell House served as the training base and home for the 1936 UW varsity eight-oared crew. This underdog team went on to win the gold medal at the 1936 Berlin Olympics, a historic triumph immortalized in The Boys in the Boat, cementing the structure's status as a monument to American athletic resilience, craftsmanship, and Pacific Northwest maritime history.