Photograph Courtesy Peter Outerbridge
Work began in 1935 on what was originally known as Roesch Memorial Stadium. The name was quickly changed to Grover Cleveland Stadium before the facility made its official NFL debut in 1937 before again changing its name for the third time to Civic Stadium which it would be known as over the next 23 years. When it was being built however... this facility was being created specifically for football and the NFL (or track). Thus it took on a completely oval  shape as this stadium was never meant to house a baseball field.