Have you read the essay “Mencken’s Conservatism” yet? It is featured at the Mencken.info homepage. There’s a huge amount of Mencken’s own words in that essay.
The two most Menckenian of Mencken’s writings are:
Other good ones include:
Lesser items, but still better than anything else:
Never before republished Mencken writings:
I shall make more of his writings available in good time. A web search will find much Menckenalia for you, but beware of yahoos.