Maximum Width Limit on Images?

It seems as though all the media (images) I upload to either posts or pages in my blog have a limit to their dimensions. None of them will be wider that a certain amount, which leaves the images different sizes. Is there a maximum width setting in the CSS that can be changed? I would like to increase the width of these images so they appear larger.

https://www.thetouringtandem.com/

Thank you,

Clayton