Sewer/main line is plugged

I've been having slow drain problems throughout my home. I know the drain problems are starting somewhere at the beginning of my main drain line going to the city utility line. Last night I removed my toilet and snaked 50 feet of line all the way out to the city's main. It didn't make any difference. I suspect I may have old clay pipes ('40s era) that are broken, thus the slow drain. Any advice or thoughts on how to handled this would be greatly appreciated. I have the sinking suspicion that I will need to replace my line the backyard. I suppose the other issue is that I don't have sufficient ventilation, but that hasn't been a problem in the past.

First of all, a DIY snake is probably not going to properly clear 50 of main drain. That's a boy sent to do a man's job. You may be right about the condition of the drain, and it's a real possibility that the drain line must be replaced, but the first thing I would suggest to have a professional plumber auger and inspect the drain. There may be some clues about its condition that he would find when running the auger. The next thing would be to have a video inspection of the drain. That would tell you what you're up against. Drain line replacement is too expensive to do without knowing for certain that it is required. Compare it to major surgery, you wouldn't have open heart surgery without having a professional diagnosis.

Thanks

That makes a ton of sense. The video could be helpful. As always, I will defer to the professionals.

Thanks for the reply.