Complex sentence: The periods from 1807 to 1858 were known as British North America's second press period, in which newspapers had already been established in six colonies and more newspapers began to spring up and spread westward.
Split into simpler sentences: The periods from 1807 to 1858 were known as British North America's second press period. At this time newspapers had already been established in six colonies and more newspapers began to spring up and spread westward.