State Route 21 (SR 21) is a state highway in the U.S. state of Washington that traverses four counties: Franklin, Adams, Lincoln and Ferry. The highway extends from an intersection with SR 260 in Kahlotus north through Lind, Odessa, Clark, Keller, Republic and Curlew before becoming Highway 41 (BC 41) at the Canadian border in Danville. SR 21 is concurrent with U.S. Route 2 (US 2) in Wilbur and SR 20 in Republic and has two diamond interchanges at US 395 in Lind and Interstate 90 (I-90) south of Odessa. Between Lincoln and Ferry counties, the roadway crosses Franklin D. Roosevelt Lake on the Keller Ferry, operated fare free by the Washington State Department of Transportation (WSDOT) and the Department of Highways (DoH) since 1930.
Since 1899, at least one segment of the current highway has been in the state highway system. In 1899, the Marble Mount Road was established and later numbered State Road 4 in 1905 and renamed to the Sans Poil-Loomis Road in 1907. In 1915, a branch to the Canadian border was added to the highway, but was removed in 1923. In 1937, the Primary state highways were established and State Road 4 became Primary State Highway 4 (PSH 4), while the former Canadian branch became Secondary State Highway 4A (SSH 4A). Another highway, extending from Lind to Wilbur, became SSH 4B. In 1964, PSH 4 was split into SR 20 and SR 21 while SSH 2A and SSH 2B also became SR 21. In 1983, a road between Lind and Kahlotus became part of SR 21.
The Keller Ferry, which travels across the Columbia River at Franklin D. Roosevelt Lake to connect the two segments of SR 21, was originally a private cable ferry operated in the early 1890s. In 1929, the Ferry and Lincoln counties unveiled a new eight-car cable ferry, named the Keller of Seattle, which served the two counties until 1930. The state highway department took over operations of the ferry in 1930 and replaced the vessel with various boats until a permanent ferry, the Martha S., was launched in 1948. The Martha S. would go on to serve until 2013, when it was retired and replaced with the more modern .
Route description
SR 21 originates at an intersection with , about east of the northern terminus of ; both intersections are in the city of Kahlotus, which is located in a narrow valley near several coulees in Franklin County. After leaving Kahlotus as the Lind–Kahlotus Road, the highway turns northeast and later west as it passes over the Sand Hills Coulee four times. Curving due north, the roadway leaves Franklin County to enter Adams County. Passing farmland in the flat landscape, SR 21 intersects and continues through an unnamed coulee to intersect Smart Road. Smart Road was the former alignment of SR 21 prior to the (US 395) interchange being built. SR 21 intersects US 395 in a diamond interchange east of Downtown Lind. From the interchange, the highway travels west and intersects Smart Road again before crossing over the Centennial Trail and entering Downtown Lind. In Downtown, the roadway is named Second, I and First Streets and serves as the main connector to other areas. After turning north to leave Lind, the road encounters the Palouse to Cascades State Park Trail and more plains before intersecting the pre-interstate alignment of (I-90) and interchanging with I-90 at exit 206, another diamond interchange. North of the interchange, SR 21 travels through more plains and a coulee to leave Adams County and enter Lincoln County.
In Lincoln County, the highway travels through farmland to encounter Odessa as Division Street, intersecting . The roadway turns northwest at Pacific Lake and reverts northwards into farmland. After temporarily turning east into more farmland, the road enters Wilbur, named Bruce Avenue. In Wilbur, SR 21 turns west, concurrent with , for before branching off north to intersect and leave Wilbur over rolling farmland. North of Wilbur, the roadway enters the top of Speigle Canyon and makes a winding descent before exiting at the floor of the canyon and nearing Franklin D. Roosevelt Lake; at , the lake is the largest in Washington. Paralleling the lake, the road then uses the Keller Ferry, an long boat used as a fare-free ferry across Franklin D. Roosevelt Lake, part of the Lake Roosevelt National Recreation Area, operated by the Washington State Department of Transportation (WSDOT) and its previous counterparts since 1930.