who established it?
Al Hanken.
The EndUp
The EndUp opened on November 15, 1973 as a differentiated version of the RoundUp, owner Al Hanken's LGBT country western-themed venue located one block north of the EndUp at 298 6th Street and Folsom. 
what is 'the endup'? It is a nightclub.
wiki:9231235
The EndUp [SEP] Al Hanken era (19731989)
The EndUp opened on November 15, 1973 as a differentiated version of the RoundUp, owner Al Hanken's LGBT country western-themed venue located one block north of the EndUp at 298 6th Street and Folsom. Mister Marcus, a writer for San Francisco's monthly LGBT magazine "Kalendar", described the EndUp's opening in his column "Man About Town":The long-awaited EndUp opened last Thursday too and you have to see it to believe it. I was lucky to get a demonstration of their quadraphonic sound system long ago. It's a big dance bar and certainly will add to the ambiance of Harrison Street. Congratulations to Al Hanken and Greg Loughner on their latest "baby".