Tax Year Prior to 2020: How do I know if my LLC is a sole proprietorship or a partnership?

How do I know if my LLC is a sole proprietorship or a partnership? Is this based on how you filed with the secretary of state? Or is it based on your articles of organization? I thought I filed as a sole propietor under the secretary of state but my husband and I act as owners in our articles of organization. My impression was that the IRS doesn't look at your articles of organization, only how you filed at the state level.