Nostalgia: The REI catalog in 1969 or '68 sold a "1-person" tent made of cotton with a nylong floor. It was radically tapered in height and width to the rear. The one in the catalog photo may have been dark blue. I purchased a similar 2-person tent that was yellow.Mine weighed about 7 pounds with A-frame front door. Eddie Bauer also sold a 1-person tent in mylon, around the same time from a different manufacturer. Gerry ultralites of the era were very small tents at minimal weight, but I think the smallest was advertised as 2-person.

Afterwards, there was a long period when REI didn't offer 1person tents. Before that, I wasn't looking at backpacking catalogs. But the British were manufacturing solo tents before WW I.