In 1969, Warren Magruder entered a partnership with Rex Galloway to begin quarry operations on a site just north of Troy, Missouri. This coincided with the expansion of Highway 61 to four lanes. This partnership lasted for 19 years, at which time Warren purchased Galloway Limestone in 1988. This deal secured two other quarry locations at Ashley, MO. and Frankford, MO. Magruder Limestone began to mine these quarries at that time, and they are still in operation today. Ashley's quarry operates with a stationary crusher and plant, while Frankford utilizes portable equipment.

During the 1990s the expansion of Lincoln County and the increase of MODOT spending accelerated production for the company over one million tons per year. Production totals have continued to increase each and every year since the company's creation. In April of 1996, a fourth quarry was opened on Highway 54 west of Bowling Green under lease from George Mehler. Also in 1996, a second crushing plant was erected in the Troy Quarry. With two crushing plants in operation, production totals climbed quickly, as well as availability of different aggregates.

In September of 1998, the first rock was crushed from the fifth Magruder Limestone quarry. This quarry is located one mile west from Highway 61 near the Auburn Junction. All five quarries continue production today, providing many locations throughout Pike and Lincoln County with high quality limestone aggregates.