Oh I haven't seen a question on Chalco here before. That's a long time span, anything you're especially interested in? I'm doing research on Domingo de Chimalpahin, Chalco's main historian, and so have done some reading on the state.

Overall, Chalco is one of the states (if not the state) we have most background on - Chimalpahin has written the largest Nahuatl corpus by a known author, and much of it is focused either on his home altepetl Chalco or on Tenochtitlan. He traces the migration of various Chalcan groups into the Valley of Mexico; their settlement into Chalco with four lower groups (calpulli) and further divisions; the Aztec conquest around 1465 and exile of Chalcan elites; and those elites' partial return decades later. The Aztec conquest here appears as a more important intrusion into local politics than the later Spanish taking over Chalco about 50 years later. In case you're interested I can mention some good readings on the topic:

• Susan Schroeder's Chimalpahin & the Kingdoms of Chalco (mentioned in the wiki article) is a classic and in-depth study of Chimalpahin's political concepts, especially for pre-Hispanic Chalco. The focus is more on political organisation but she discusses historical developments as well.

• In case you read Spanish, Tomás Jalpas Flores has done probably the most detailed work on Chalco, pre- and esp. post-colonial periods. In La sociedad indígena en la región de Chalco durante los siglos XVI y XVII he discusses politics, economy, nature among other topics.

• In case you want to dig deep - Chimalpahin's complete works I think are only translated into Spanish so far, but quite a few into English too. For pre-Hispanic times the most relevant would be the Codex Chimalpahin, edited once more by Susan Schroeder.

I probably won't manage to write something more detailed until after the weekend unfortunately. But if you let me know some more specific interest on Chalco I can gladly get back to you about it here.