MD 24 was one of the original state-numbered highways designated in 1927. The state highway originally began at MD 23 in Forest Hill and followed its current course along Rocks Road north to Bush's Corner, then followed Pylesville Road (which later became MD 165) through Pylesville to the Pennsylvania state line at Cardiff. The portion of Pylesville Road between Graceton Road (now MD 624) and the village of Pylesville was paved with macadam by 1910. MD 24 from just north of Forest Hill to Graceton Road was built with a wide concrete surface in four sections, with construction underway by 1917 and completed by 1921. The state highway just north of Forest Hill and the highway from Pylesville northeast to the state line were completed with a macadam surface by 1923.