The Vostok spacecraft used by Yuri Gagarin seems to have had an "ejection seat". The Soyuz launcher has an escape tower, which at least once saved its crew. The space shuttle of course did not have any other option than to land the orbiter intact. Were the 135 space shuttle launches the only times when astronauts did not have a launch escape system to rely on if their spacecraft disintegrated?
US Gemini capsules had ejection seats, not escape towers.
Shuttle had ejection seats (commander and pilot only) for the first 4 flights (albeit with limited useful envelope: close to launch and landing). And after STS-51L the shuttle had a bailout system (although it was useful in only a minuscule number of possible scenarios.)
Shuttle bailout testing video:
Screen shot of shuttle display with bailout mode engaged
1$\begingroup$ The shuttle bailout capability would be useful in far more than a "miniscule" number of possible scenarios - the crew would have been saved by bailing out in literally every scenario where the orbiter could be gotten into at least semi-stable gliding flight but would be out of range of any landing site. $\endgroup$– VikkiFeb 20, 2019 at 4:08
2$\begingroup$ Of the total number of all possible aborts, what % would the pole be useful in? I have participated in the simulation of thousands of such aborts with the crew and flight controllers, and the pole was in play a handful of times. You might have better info though. $\endgroup$ Feb 20, 2019 at 13:54