The establishment of a post office on April 1, 1906, marked the formal founding of Clair as a community in Saskatchewan, with George W. Heller serving as the first postmaster. The town was named for his daughter Clair Heller. This administrative milestone preceded significant infrastructure development and reflected early efforts to organize settlement in the region.

The arrival of the Canadian Northern Railway in 1908 catalyzed rapid growth, positioning Clair as a key railway town and facilitating access for homesteaders drawn to the fertile prairie lands. The railway's extension through the area promoted agricultural opportunities, leading to the construction of essential facilities by the 1910s, including grain elevators for handling crops, a general store for daily supplies, the existing post office, a hotel for travelers, and various small businesses catering to settlers. These developments made Clair a vital hub for pioneers in the Quill Lakes region, supporting the influx of immigrants seeking farmland.

By the 1920s, the town's population had grown significantly, fueled by railway advertising that highlighted the potential of the surrounding grasslands for wheat farming and homesteading. This early expansion underscored agriculture's foundational role in sustaining the community's economy.

In the mid-20th century, Clair emerged as a vital grain shipping hub in central Saskatchewan, bolstered by the presence of multiple wooden grain elevators that stored and loaded crops from surrounding farms for transport via the Canadian Northern Railway line. By the 1940s and 1950s, these facilities, operated primarily by the Saskatchewan Wheat Pool, supported a local economy centered on agriculture, with the hamlet sustaining essential community services including schools, churches, and small businesses.