I remember it well, but I was only 10 years old at the time, so had no real understanding of the significance or future implications of the event. I grew up in the "rust belt" where every river had a steel mill or other industrial facility right on the water, and industrial accidents and occupational injuries/illnesses/fatalities were just a part of life for those who worked there.
Later in life (while working in the chemical/phamaceutical industry), I participated in an "amnesty" program with the EPA (working in conjunction with a group of major chemical and industrial manufacturing companies) to audit environmental/worker health and safety records from facilities (many still in operation) dating back as far as 1918.
These companies actually did keep fairly detailed records (even back then), but there was no EPA or any other reporting/regulatory agency at that time. The purpose of the program was to collect and evaluate this historical data, and the incentive was no threat of penalties/retribution to the participating companies for "sins" of the past. For those curious, the program was the TSCA Section 8e compliance program (falling under the Toxic Substances Control Act of 1976). The EPA (as we know it) was actually not formally established until December, 1970, OSHA, not until April, 1971.
I spent the better part of over a year poring through some of these records, and was just "shocked"--not by the horrendous environmental "disasters", workplace fatalities and work-related illnesses, but also by how legitimately concerned the companies were--way back into the 20's through early 60's. In most cases, it was a matter of "we just didn't know"--yet. They were working toward not having fish-kills in the river, and if people were getting sick/dying as a result of exposure to a particular process, they were doing their best to provide medical care and pension compensation to those affected--without a room full of greedy lawyers waiting in the wings.
I am, by no means, a staunch defender of the current state of the industry, but having read tens of thousands of pages of hand-written/hand-typed internal memos, reports, scientific studies, and directives to actually believe that it was mostly about all we didn't know or could even remotely anticipate, at the time.
By 1969, yeah, that (the Cuyahoga River fire) was a "travesty", and shouldn't have happened, but it serves its place in history.