The project began with an invitation. Washington state asked Native American tribes of the region -- the Chinook, Umatilla, and Nez Perce among them -- to participate in commemorating the bicentennial of Lewis and Clark's 1805 journey to the Pacific. Lin was brought in to design installations that would mark key sites along the expedition's route through the Columbia River Basin. But the Confluence Project was never a simple celebration of the expedition. Lin drew text from William Clark's journals -- his meticulous species lists, his observations of landscape and weather -- and carved them into planks and pathways. At the same time, she grounded each installation in the indigenous traditions of the place: Chinook praise songs, Nez Perce blessing ceremonies, the deeper history that the journals never recorded. The result is an art project that holds two stories simultaneously, without pretending they are the same story.

The first installation, at Cape Disappointment State Park near Ilwaco, Washington, was completed in 2005 and dedicated the following year. At the ocean-facing edge of the park, a walkway of crushed oyster shells leads past an open-air amphitheater to a circle of cedar driftwood columns. A Chinook praise song is inscribed along the pathway. Nearby, planks etched with an index from Clark's journals list the species the expedition documented at this site -- a catalog that reads like an inventory of a world the explorers were only beginning to understand. The installation does not explain itself. It does not tell you what to think about Lewis and Clark, or about the Chinook, or about the collision between their worlds. It gives you the materials -- the words, the shells, the wood -- and lets the landscape do the rest.

Lin collaborated with landscape architect Johnpaul Jones, a Native American architect of Cherokee and Choctaw descent, to design installations that did more than commemorate. They restored. The Vancouver Land Bridge, completed in 2008 at Fort Vancouver National Historic Site, is a grass-covered pedestrian bridge that reconnects the historic fort with the waterfront, physically healing a landscape that a highway had severed. At the Sandy River Delta in Oregon, Lin designed a bird blind -- a structure that conceals human observers while framing views of the wetland habitat -- completed in 2008. The blind doubles as sculpture, its wooden slats filtering light and sound, turning birdwatching into something contemplative. At Sacajawea State Park in Pasco, Washington, a 2010 installation marks the confluence of the Snake and Columbia rivers, a gathering place for Native peoples long before Lewis and Clark arrived. Each site encompasses restored land: the project has worked across more than 15,000 acres of state and federal property, redesigning spaces so that the first thing a visitor connects with is the landscape itself.

The easternmost installation is the Listening Circle at Chief Timothy Park near Clarkston, Washington, where the Snake River cuts through the canyon country approaching Hells Canyon. Nez Perce elders helped choose the site, and the installation -- designed by Lin with landscape architects from Greenworks -- consists of low stone benches arranged in three concentric arcs. There is nothing to read here, no text carved into surfaces. The benches are oriented to frame the river, the canyon walls, the sky. The design was inspired by a Nez Perce blessing ceremony, and its purpose is exactly what its name suggests: listening. The sounds Lin intended visitors to hear are not only the river and the wind but the inaudible echoes of the past -- the people who fished these waters, the languages spoken on these banks, the histories that persist in a landscape even when no monument marks them. It is the quietest kind of memorial, asking nothing of visitors except stillness.

One planned installation remains incomplete. The Celilo Falls site, intended to mark the place where a great waterfall on the Columbia was submerged by the construction of The Dalles Dam in 1957, has been on hold. Celilo Falls was the oldest continuously inhabited site in North America, a place where Native peoples had fished for over 15,000 years before the dam drowned it beneath a reservoir. The loss is still raw for the tribes of the region, and the complexity of commemorating something that was deliberately destroyed -- and that some people alive today remember -- has slowed the project. Lin's Confluence Project is not finished, and perhaps that incompleteness is appropriate. The Columbia River system is itself unfinished, still being shaped by tectonic forces, still being fought over by the people who depend on it. The art along its banks does not try to resolve these tensions. It marks where they converge.