You can remember the meaning of 芝加哥 with this easy mnemonic:
I'm allergic to 芝 (Zoysia pungens), but people from Chicago always add (加) them to their lawns. My brother (哥) became so allergic to them, he moved out of Chicago!
Using mnemonics to remember the meaning of Chinese characters like can have an enormous impact on how long to learn Mandarin it takes.