Complex sentence: Wellington grew fast and by 1874 the School in Wellington had 90 pupils, and by the 1890s the town, with 5,000 residents, was the second most important city on Vancouver Island (after Victoria, the capital).
Split into simpler sentences: Wellington grew fast and by 1874 the School in Wellington had 90 pupils. By the 1890s the town, with 5,000 residents, was the second largest city on Vancouver Island (after Victoria, the capital).