Complex sentence: He served as Minister of Public Works and Minister of Municipal Affairs--the first person to hold the latter position in Alberta--in the government of Arthur Sifton; when Sifton left provincial politics in 1917 to join the federal cabinet, Stewart was named his replacement.
Split into simpler sentences: He served as Minister of Public Works and Minister of Municipal Affairs--the first person to hold the latter position in Alberta--in the government of Arthur Sifton. When Sifton left provincial politics in 1917 to join the federal cabinet, Stewart was named his replacement.