It's a bit fear-mongery. Untreated tap water was dangerous; at the same time, the brewery might benefit financially from scared people who might consider beer as the safest alternative to tap water.
It doesn't make Mayor Lachmund's decision to veto municipalizing the water supply look very good. The ad really makes it look like it was truly possible that brewers and hopsgrowers would feel a pure source of tapwater might threaten their beer sales, however compromised by crappy water the beer might be. If you mask it with enough hops, few would notice.
While I still haven't found any direct evidence for a Lachmund conspiracy against pure water, there's certainly a suggestive penumbral shadow.
In the face of growing sentiment for Prohibition, the ad is also direct about the sensory allure of beer - the lively prickle from carbonation and the "stick" from alcohol.
Moreover, the ad's themes cast an interesting light on early advertising: local boosterism, quasi-scientific precision, the reasonableness of the flattering confidence-man, and the commercial preference for selling a product - consumerist progress - instead of investing in solutions - infrastructure progress. This was politically a mixed time, a transition between the gilded age and the progressive era, and the rhetoric of "progress" looks a bit like "greenwashing" today.
I find it a fascinating document.
The Salem Brewery Association plant for the brewing and bottling of beer and manufacturing of ice is one of Salem's most important industries. During the past five years this business has grown from a very small, old-fashioned brewing plant to one of the most modern enterprises on the coast. The name "Salem Beer" is a familar household term over most of California and Oregon. It has gained enviable reputation throughout this western country and is a welcome beverage in numerous families. Over one million bottles of Salem beer were consumed during the past year. As each bottle is decorated or marked with the trade mark label, showing the beautiful State Capitol building, this fact alone has consequently served as a medium of advertisement for the city of Salem of considerable magnitude and value. Thousands of people know of Salem, as the home of Salem beer.
WHAT IS BEER
To meet "a long felt want" of mankind in the form of a mild, carbonated, alcoholic, stimulating, cooling, palatable, refreshing tonic and thirst-quenching drink, the beer of today is the best drink in the world.
Just observe for a moment how beer is made up. First and foremost, about nineteen-twentieths of a glass of beer is just cold water.
Now, cold water "plain" and "straight," which has not been boiled, is a very dangerous drink. Positively hundreds of thousands of poor victims of typhoid fever have been sent to premature graves in these United States by the typhoid germs which are taken into the system almost exclusively from drinking water.
But the water of beer has invariably had all dangerous germs killed out of it by a vigorous two hours' boil. If we were to drink this boiled water straight, the remedy would be worse than the disease; for of all "flat, stale and unpalatable" drinks, boiled water, deprived by boiling of its natural content of sparkling air, is the flattest. But, in the case of beer, here comes plenty of carbonic acid gas to put new life into the boiled water. The process of fermentation cuts up the sugar of the beer wort into a little alcohol and , by bulk, a good deal of carbonic acid gas. So, then, we have so far found in our beer the two constituents, water and carbonic acid gas, which together make "plain soda water," neither more nor less; and then we find that our fermentation has given us also a little alcohol, about one-twentieth part of the whole, so that now our glass of beer is simply a glass of "soda water" with a "stick" in it.
And yet, without this little dash of alcohol, beer would not be beer at all, beer would not be used at all.