system
Given the following post, respond as if you're commenting on Reddit:
human
How did they originally get oxygen to the International Space Station?
gpt
The glib answer: On rockets.

The longer answer: It was flown up through various means (tanks of compressed air and so forth. But one of the other sources during the shuttle era was bags of water delivered from the shuttle to the ISS. The fuel cells on the shuttle produced water as their "Exhaust" which was collected and delivered in bags to the ISS. This was used for both domestic purposes (drinking, cleaning, etc...) and run through electrolysis to produce oxygen to breath. The excess hydrogen was dumped overboard.