The colonization era started in 2150 when the TSF was founded. It ended in 2475 when the rebellions officially started and the TSF focused on destroying them instead of colonizing planets. The colonization era is often considered the first golden age of humanity as a space faring race. It is estimated 400-500 colonies were founded in this era. The human population more than doubled during this period.
For the most part this era was devoid of war. Humanity was to distracted with expanding its borders and economy. The population of Earth during this period was the lowest it had been in years. Many had left for the colonies, for a new beginning, a new life.