If a historian was writing biography about YOU, what might be one good primary source for your life and times?

Social Media, information that the government has on you, and information that other firms have on you.

Explanation:

Social Media would provide the historian with very reliable and very personal information about your search and interaction habits on the internet, including your tastes, the people who you talked with online, and the intensity of use.

The government also has information of its citizens that would be useful to an historian, like tax records, social security information, and whether you have a criminal record or not.

Finally, private businesses also keep data on their customers, and this data would contribute to the historian research if the historian is able to have access to it.