According to the United States Bureau of Labor Statistics, the state of California employed an estimated 2,560 locomotive engineers as of May 2010. These engineers operate large locomotives to carry commercial and industrial cargo as well as traveling passengers. They must not only posses the knowledge of their routes and skills necessary to maintain and operate the equipment, but must also obtain licensing in California to legally drive steam boiler trains with more than five horsepower.

Choose the type of license you wish to obtain. For those operating boilers rated up to 500 horse power, the "Steam Engineer - 500 HP" license will do. California also offers the "Steam Engineer - Unlimited HP" for engineers operating boilers rated over 500-horsepower.

Obtain the minimum requirements necessary to qualify for the licensing exam. You can only take the "Steam Engineer - 500 HP/Unlimited HP" licensing tests after at least one year of full time steam engineer work or three years on the job as a water tender, assistant engineer or fireman.

Fill out the licensing exam application for the city in which you will work and pay the fee. Along with the application form, provide one passport-size color photo and a completed work history sheet. Include experience related specifically to bier operation. The application fee in Los Angeles was $54 in 2008, but may vary depending on the city. You must notarize applications submitted by mail.

Receive your scheduled exam time. The appropriate office will inform you of this date by mail and the test must be taken within six months of application validation.

Take the exam. You must provide identification such as a passport or driver's license when you arrive. The test lasts one to one and a half hours and contains two sections. The first is a multiple choice written exam with 50 questions focused on the operation of steam boilers and equipment. The second section consists of an oral interview after passing the written exam. Applicants must answer correctly on 70 percent of the questions in the written exam to pass.

Retake the test in the case of failure on the first exam. There is no repeat fee to retake the test but you must typically wait at least four weeks.

Maintain your steam engineer license by renewing annually. The renewal fee in Los Angeles in 2008 was $27.50.