Leo Nonnenkamp was born on July 7, 1911, in St. Louis and picked up the nickname “Red” at some point along the line. He never played baseball in school and first played semipro baseball, at the age of 18, in the St. Louis Muny League in the summer of 1929. His .521 average earned him an invitation to join the St. Louis Cardinals’ baseball school at Danville, Illinois.

Leo was signed to a contract and assigned to the Waynesboro Red Birds in the Blue Ridge League, playing Class D ball. He went through a couple of affiliate transactions during the offseason. He was on the roster of Houston and then Springfield, but by the time 1931 began he’d been advanced to Class C, playing in Pennsylvania’s Middle Atlantic League for the Scottdale Cardinals. 

He was also on the roster of an independent team which began the season in Jeanette, moved and became the Beaver Falls Beavers. In the off-season of 1931-32, Leo became part of the Pittsburgh Pirates system and was given a ticket to Tulsa in 1932, jumping to the Class A Western League. He was hitting a spectacular .391 over his first 16 games when he broke his ankle.

He began 1933 with Tulsa but the Oilers needed some right-handed hitting and Leo was asked to go to El Dorado, Arkansas. Not surprisingly, he did better for the Class C Dixie League El Dorado Lions, batting .336. He was rewarded with a late-season call-up to the Pirates, but he did not get much playing time. The Pirates optioned him to Little Rock (Class A) for the next couple of years. 

Leo played with Little Rock in 1936 and 1937 hitting .326 and .332 respectively. Little Rock had meanwhile become a Boston Red Sox farm team. Pittsburgh was out of options by this time and so sold his contract outright to Little Rock. He was voted MVP of the Southern Association in 1936. The Travelers led the league in 1937 and beat New Orleans in the playoffs and  Leo was the unanimous choice as the league’s Most Valuable Player.

During 1938 he made the big-league club, and Ted Williams did not. Williams was sent to Minneapolis for more seasoning and Leo joined the Red Sox as their fourth outfielder, getting into 87 games, for a total of 180 at-bats and hit .283.

In 1939, Ted Williams came up and Leo was an outfield backup. With his .300 average in pinch-hit duties, he was kept on the team, accumulating 75 at-bats in 58 games, and hitting .240, filling in as needed. Leo didn’t know it yet, but the handwriting was on the wall. His major-league career was almost over, because the Red Sox had another outfielder coming up in their system named Dom DiMaggio.

The Sox purchased Lou Finney from Philadelphia, and was going to use him in right, Cramer in center, and Williams in left field. All three Sox regular outfielders hit over .300 in 1940. Leo was even more frustrated than in 1939, playing in only nine games for the Red Sox during April and May, exclusively as a pinch-hitter. In June, the Red Sox optioned him to Louisville and brought up Stan Spence. 

Before the end of the month, Louisville swapped him with Newark. He had hit .294 for Louisville, albeit in only 17 at-bats, but got more playing time in Newark. In September, the Red Sox sold his contract outright to Newark and he played for them during the entire 1941 campaign.

Early in 1942, the Kansas City Blues bid for his services and Leo joined the American Association and had a subpar season at the plate.

In the spring of 1943, Leo was taken into the Navy, and right after finishing boot camp at Great Lakes Naval Training Station, found himself playing for the famous Great Lakes team. He served in the Navy for the duration, stationed on New Caledonia in the Pacific for 1944 and 1945. Having missed three seasons of pro ball, he returned with the Little Rock Travelers in 1946. It would be his final year. The Travelers had him help run their baseball school in March, but this was the end. He worked for many years as a post office mail carrier after baseball.

Leo Nonnenkamp was inducted into the Arkansas Sports Hall of Fame in February 1993 and passed away, at age 89, on December 3, 2000, in Little Rock, Arkansas.