Some of the plain brown sleeves had simple logos on them but nothing like what we think of as "album art" today. More here.
In the year 1939, Alexander Steinweiss proposed to Columbia that maybe original artwork might spruce up those plain brown 78rpm sleeves. Before that an ornate font or logo was as edgy as the "art" got. The new look moved units. as soon as labels realized that album art can drive sales, all albums had art. People say today that labels are hard to adapt, but that's not true. If they can see the money, they move. More here. The first album featuring actual cover art was “Smash Song Hits by Rodgers and Hart” sold records. [Anyone have a scan?] That sealed the deal.
Eight years later Steinweiss invented the paperboard jacket that protected vinyl records from scratches and chips. it also made a more robust canvas for the artwork. The previous paper sleeves were too delicate. His innovation has been the industry standard for half a century. He often signed his work, something that rarely happens now. More on that here.
He was the art director for Columbia at the age of 23, that year, and continued to do album art until 1973 when he went into semi-retirement. but between 1939 and 1945, he designed all the covers for the label. Around 1950 he started doing art for Remington records, Decca, London and Everest.