A TALE OF TWO EASTSIDES
In Los Angeles, usage of the term "Eastside" varies depending on the speaker. To most Angelenos -- especially Latinos -- "The Eastside" refers to a group of neighborhoods immediately east of the LA river: Boyle Heights, Brooklyn Heights, City Terrace, East Los Angeles, El Sereno, Happy Valley, Hillside Village, Lincoln Heights, Rose Hills, and University Hills.
THE (HISTORICALLY) BLACK EASTSIDE
Pendersleigh & Sons' Official Map of South LA's Eastside
The other Eastside is in South LA. This Eastside was historically the main area that LA's black residents were required to live until the middle of the 20th century. It should be noted that when people speak of this region -- though they're implicitly referring to the East Side of South Los Angeles -- that reference to this area as "the Eastside" likely pre-dates the modern version of communties east of the river. Check out The Eastsiders, a documentary about South LA's Eastside between 1920 and 1965.