Is it legal for a US employer to turn me down because of my age?

No, if you are 40 or older and age is the reason. The US Equal Employment Opportunity Commission (EEOC) explains that hiring decisions must not be based on age for people aged 40 and over, along with other protected traits such as race, sex, religion and disability.

The EEOC also says that information which could reveal those traits is not relevant to whether someone is qualified. That is one reason many US job seekers leave birth dates and personal details off their resumes.

For your resume, this means:

• You do not need to include your date of birth or age.
• Focus on qualifications, recent experience and results.
• Keep your dates accurate; protection from discrimination does not change honesty rules.

If you believe you have faced age discrimination, the EEOC is the official place to learn about your options. This answer explains resume presentation only and is not legal advice.