Conversation so far:
How did this company come about?
Carnegie worked to develop several iron works, eventually forming the Keystone Bridge Works.
What had he been doing previous?
Carnegie invested $40,000 in Story Farm.
What was Story Farm?
oil wells on the property sold profitably.
How much did they make from the oil?
the farm yielded over $1,000,000 in cash dividends.
What other items were they making?
Carnegie worked with others in establishing a steel rolling mill.
What else were they producing?
Carnegie worked to develop several iron works.

Question: What else were they doing to grow the business?
Self-contained rewrite: Besides developing several iron works, what else was Andrew Carnegie doing to grow the business?