Sounds like the story of the chicken or the egg. Eastern Gas & Fuel in Everett Mass. was an integrated coke/gas producer. from the 30s through the 50s. Integrated here means the facility produced coke (~2.5M annual tons), using soft coal, for Mystic Iron merchant pig blast furnace on the property, foundries all over New England, and retailers of home heating coke. It was rail served by both the B&A (40-car coke trains daily) and B&M (25 cars daily) for distribution to local retailers and foundries. The coking process releases huge quantities of coal gas which can be used for a number of applications. Gas was first processed in the byproducts plant for removal of tar and other toxic chemicals. The primary application here was to supply Boston Gas with large volumes of home cooking gas which was processed (cleaned) in a large facility next to the coking ovens and stored in huge storage tanks. This gas served Boston and a number of northern suburbs. Secondary use of the gas was to heat the coking ovens and the blast furnace stoves. There were a number of facilities like this across the country (without the blast furnace) whose primary function was to produce gas. I believe it's true, though, that the highest volume of coke was produced for the steel industry. It's interesting to note that coke was a byproduct of many manufactured gas producers but not in high enough volume to market on a large scale. On top of that, some manufactured gas processes used coke as fuel.
Norm Larkin