For 40 years, Bill Lavicka fought noisily to save old Chicago churches, houses and other neighborhood architecture from the wrecking ball. He worked quietly to restore buildings all over the city, rehabilitating dozens in his whimsical style.

One day in 2004, Mr. Lavicka lamented that for 17 years he had been maintaining his odd and out-of-the-way Vietnam Survivors Memorial on Oakley Boulevard, and he was starting to worry about who would look after it when he was gone.

“How many more 17 years do you think I got left?” he said.

This year Mr. Lavicka, an outspoken Chicago activist, artist and real estate developer, now 66, received a diagnosis of Stage 4 colon cancer, and he is counting time in far smaller increments....