From the time you begin applying for a CDL, a number of state and federal agencies begin collecting data. For instance if you change addresses, move to another state, get a ticket in your personal car or have your CDL suspended, it is all recorded and added to your driver record.
State laws differ regarding driving records and how long drivers, insurance companies and employers can request a copy of the record for but it appears that many employers can look back at your driving record for the past 10 years. Employers may differ on how long they look back though depending upon their internal guidelines.
From the information we have read many employers want a CDL driver to have a good driving record with no more than three moving violations (minor such as speeding, running a stop sign, etc.), and/or accidents in the last three years as a median qualification, but there are different allowances in this area from company to company.
Some companies are stricter while others are more lenient. A DUI/DWI on the driving record in the past 5 years is a disqualification, as well as reckless driving, leaving the scene of an accident, or fleeing a police officer. Most companies check driving records of employees for as far as 10 years back to make certain the person has a "good" driving record.
Federal Motor Carrier Safety Administration (FMCSA) notes that every motor carrier must have a qualification file for each regularly employed driver. In this file they must include the driver's driving record for the preceding three years, though an employer can look farther back.
At least once every 12 months, a motor carrier must review the driving record of each driver. A note stating the results of this review shall be included in the Driver's Qualification File.
Keep in mind also that before issuing a CDL to any person, the issuing State shall request the complete driving record from all States where the applicant was licensed within the previous 10 years to operate any type of motor vehicle.
If you want to find out if your state limits how far back an employer can check your driving record, check with your state's Department of Motor Vehicles.