Cy-Fair Volunteer Fire Department (Texas) : The largest volunteer fire department in the United States

Cy-Fair VFD is a combination department utilizing both volunteers and paid crews. During the standard work week and work day, six engines, one heavy-rescue truck, and one ladder truck are manned with a paid staff in order to provide a timelier response. Cy-Fair's Medic Units are staffed with full-time employees 24 hours a day, year-round.

In the late 1950’s, the Cypress area was served by the Jersey Village, Houston, and Fairbanks Fire Departments. After a home was destroyed by fire due to a 20-minute response time by the first unit, the need for a closely located fire department became apparent. Recognizing the need, the Cypress Civic Club held a meeting to check into the Fairbanks Fire Department. In 1961, the Fairbanks Fire Department charter was changed to become the Cypress-Fairbanks Volunteer Fire Department.

As fire coverage needs grew in the Cypress area, the department charter was again changed in 1962 to become the Cy-Fair Volunteer Fire Department. The department went through another change in 1980 when an 80-square mile section of Cy-Fair was charted as the Cypress-Creek Fire department. This area had 18,000 residents and 5000 homes. Sixteen (16) men that were part of Cy-Fair became the Cypress Creek Fire department.

According to wikipedia