Original sentence: " East County, geographically, is the end of the Santa Monica Mountains, in which the Conejo Valley is located, and where there is a considerable decrease in elevation.A majority of these communities are in the Conejo Valley, one of the most affluent areas in the United States.Communities which are considered to be in the East County are Thousand Oaks, Newbury Park, Lake Sherwood, Hidden Valley, Santa Rosa Valley, Oak Park, Moorpark, and Simi Valley.East County consists of all cities east of the Conejo Grade, known locally as "The Grade
Edited sentence: " This area, geographically, is the end of the Santa Monica Mountain Range, in which the Conejo Valley is to be found, and where there is a large change in elevation.A majority of these communities,  Thousand Oaks, Newbury Park, Lake Sherwood, Hidden Valley, parts of Santa Rosa Valley, and Oak Park are in the Conejo Valley, one of the most affluent areas in the country.Communities east of this area which are considered to be in the East County are Thousand Oaks, Newbury Park, Lake Sherwood, Hidden Valley, Santa Rosa Valley, Oak Park, Moorpark, and Simi Valley.East County consists of all cities east of the Thousand Oaks / Camarillo city boundaries, which is known as the Conejo Grade, or simply "The Grade