Final answer:
The completion of the Canadian Pacific Railroad in 1885 was a key government measure that attracted new immigrants to Western Canada, as it enabled easier settlement of the prairie provinces and contributed to the country's industrialization.
Step-by-step explanation:
A government measure that attracted new immigrants to Western Canada in the early 20th century was the construction of the Canadian Pacific Railroad, which was completed in 1885. By linking eastern and western Canada, the railroad facilitated the settlement of the prairie provinces and supported the country's industrialization. It was constructed largely by European and Chinese immigrants, which underscores the dependence of the region's rapid business growth on immigrant labor. Moreover, the completion of other transportation and communication networks, such as railroads, telegraphs, canals, and steamships, further encouraged migration by making it easier for settlers to claim land and access new areas.