Complex sentence: In the early 1900's The Rancho Ricon de Las Salinas y Potrero Viejo became known as the Outer Mision, it covered the South Eastern portion of San Francisco, it included everything South of the Mission District, all the way to the county line.
Split into simpler sentences: In the early 1900's the area known as Rancho Ricon de Las Salinas y Potrero Viejo specifically everything south of the mission district became known as the Outer Mission. The Outer Mission covered the South Eastern portion of San Francisco, it included everything South of the Mission District, all the way to the county line.