Windy City (GTA 5 Chicago) is a map modification developed by Dekurwinator, FV Mods, Jdmimport and Lozano 71.  

1.12 changelog:

1. 3 billboards and railing on Lake Shore Drive. Billboards feature Grand Senora Desert tourism Advertisement, Cluckin' Bell and a vehicle sale commercial.
2. Cargens (random parked vehicles) and fencing on west part of the map.
3. Traffic path node (YND) fixes close to The Trump Tower area with 2 intersections trimmed and fixed. Additional traffic with detailed lanes ("HD Traffic") added to loop around the adjacent block.
4. Michigan tunnel collision fix, no more invisible wall glitches.
5. Marina Tower now has added and corrected window textures that reflect at day and night using spec shader.
6. Rearrangement of roadblock barriers and addition of more instances to prevent players to venture into non-playable areas of the map. A "floating" road barrier near the big crane has been corrected and positioned accordingly.
7. Navmesh (YNV) fixes which prevent NPC's from spawning and falling into their death near Milennium Park, building near The Trump Tower and patched peds that used to spawn within concrete blocks on Lake Shore Drive and within the area where the new parking cargens and railing was added.

MLO Interior addition has been made to the mod and is already present in the mod files but since it's not normally accessible, location and details are not revealed at this time. Best to treat it like a Easter Egg ;)

Legal: All content belongs to Codemasters, Rockstar Games and Take-Two Interactive.
Codemasters
https://www.codemasters.com/
Rockstar Games
https://www.rockstargames.com/
Take-Two Interactive
https://www.take2games.com/

GTA 5 Chicago, Windy City, Windy City Christmas Edition use a base map mod for GTA 5 called Race Map Pack by Dekurwinator. https://www.nexusmods.com/gta5/mods/169?tab=docs

For any game instability and, or crashes try installing these mods:
Gameconfig for Limitless Vehicles by F7YO
 https://www.gta5-mods.com/misc/gta-5-gameconfig-300-cars
 Heap Limit Adjuster by FiveM Systems Division
 https://www.gta5-mods.com/tools/heap-limit-adjuster-600-mb-of-heap
 Packfile Limit Adjuster 1.1 by Unknown Modder
 https://www.gta5-mods.com/tools/packfile-limit-adjuster