HOUSTON Fire Dept. Challenge Coin. This is a great looking Houston Fire Dept challenge coin. Coin is about 1 9/16" in diameter and raised lettering on both sides with a reeded edge. Reverse side is a highly polished gold plated. Coin is contained in an acrylic air tight holder. City of Houston Fire Department (HFD) is the agency that provides fire protection and emergency medical services for the city of Houston, Texas the fourth largest city in the United States. HFD is responsible for preserving life and property for a population of more than 2 million in an area totaling 617 square miles (1,600 km2). The department is the largest fire department (by number of personnel) in the state of Texas. The Houston Fire Department got its start in 1838 with one station known as Protection Company No. 1. By 1859, the volunteer department had grown to three stations. After 57 years of service, Houston converted the department over to all paid members.