I found this following information on ElvisNews. I think that after this 1956 Concert Tupelo named the September 26th the Elvis Presley Day and celebrate it since then.
Before finishing the film 'Love Me Tender', Elvis played a triumphant homecoming in Tupelo at the Mississippi-Alabama Fair and Dairy Show, his first appearance there since he'd sung 'Old Shep' a lifetime ago. 'The fair this year has the strongest grandstand lineup in years,' boasted the Tupelo Daily Journal. 'It has Elvis Presley, the current biggest drawing card on the American entertainment scene; and it has an outstanding lineup of livestock and agricultural exhibits.' A wire report covering Elvis's September 26th show ran the headline: 'Tupelo Ain't Nothing But A Town Agog.' The Governor and Mayor praised him from the stage, and Elvis said of his return, 'It's the greatest thing that's ever happened to me.' A fan rushed the stage while Elvis was singing 'I Got A Woman.' He fell backwards and laughed, and two police officers grabbed the sixteen year old and carried her kicking from the stage. When she was later asked why she'd stormed him, she replied, 'I want him and I need him and I love him.'