Complex sentence: In 1856 the Humboldt Harbor Light was built on the north spit, in 1872 a bell boat was added, and two years later, a steam whistle replaced the bell to assist mariners during times of dense fog.
Split into simpler sentences: In 1856 the Humboldt Harbor Light was built on the north spit. In 1872 a bell boat was added, and two years later, a steam whistle replaced the bell to assist mariners during times of dense fog.