Complex sentence: Early in its beginnings, the School of Mines was focused primarily on mining and metallurgy, but by the 1920s, had expanded into civil, electrical, mechanical and chemical engineering as well as chemistry, physics, mathematics and geology.
Split into simpler sentences: Early in its beginnings, the School of Mines was focused primarily on mining and metallurgy. By the 1920s, the school expanded into civil, electrical, mechanical and chemical engineering as well as chemistry, physics, mathematics and geology.