Baer was born in West Virginia and graduated from Princeton University. He married Isabel Aloe and joined her father’s company, A. S. Aloe Company, a surgical supply business, in 1927. When his father-in-law died two years later, he became president. He led the company through the depression and merged with Brunswick Corporation in 1959.

Always a civic leader, Baer was a member of 50 organizations when he retired in 1961. His most important contributions came from his involvement with the St. Louis Zoo, where he was president of the Zoo Board in the late 1960s and early 1970s, started the Children’s Zoo and the Zoo Railroad, and led efforts to pass the Zoo-Museum Tax District. He sponsored many sculpture shows and the Schoenberg Fountain at the Missouri Botanical Garden. With his mother-in-law, Mrs. Louis Aloe, he was a major contributor to the Carl Milles fountain in Aloe Plaza.

Baer won the Legion of Merit for his war efforts in 1945, the St. Louis Award in 1969, and the Globe-Democrat Man of the Year award in 1971. He was the first Jewish member on many boards of directors, and one of the first two Jewish members of the St. Louis Club. His autobiography is titled, "Saint Louis to Me: Footnotes on 50 Years."