The concept had a precedent. The original Lennon Wall in Prague was created after the murder of John Lennon in 1980, gradually filling with Beatles lyrics and expressions of resistance to the communist regime of Gustáv Husák. By 1988, a year before the Velvet Revolution, that wall had become a symbol of dissent through art. The Hong Kong version took the same idea and adapted it to a different crisis: the demand for universal suffrage in the territory's elections. Over ten thousand Post-it notes accumulated on the staircase wall — epigrams, poems, lyrics, foreign words, and hand-drawn graphics. The scale of it surprised everyone, including the people who started it. When the banner reading 'Lennon Wall Hong Kong' went up on the outside wall, the connection was named and the landmark was made.

Police arrested a fourteen-year-old girl for drawing flowers on the wall with chalk. They threatened her father with the removal of custody and did not release her back to her family until twenty days later. The pictures of her drawing flowers circulated widely on social media, and she became known as "Chalk Girl" — 粉筆少女. Her lawyer, Patricia Ho, stated that the government response was "disproportionate" and that "police are using whatever mechanism they can think of to stop teenagers from participating in any protest." The case concentrated something that the wall itself had expressed diffusely: the gap between what authorities said was permissible and what people felt they had the right to do. A child drew flowers. The state responded as if it mattered enormously. Perhaps it did.

When police cleared the occupied areas in December 2014, most of the artworks were removed before the operations began. Citizens tried to rebuild immediately: on 20 December, they stuck posters reading "It is just the beginning," "We will be back," and "Umbrella Movement" on the staircase wall outside the Central Government Offices. Staff from the Leisure and Cultural Services Department tried to stop them. The police noticed but did not intervene. Sensing the loss that was coming, one organizer had already created an online version of the wall, digitizing approximately ten thousand Post-it notes into an archive. The physical wall could be cleared. The record of it was harder to erase.

The phrase the 2019 protesters used was 遍地開花 — "blossoming everywhere." Beginning in June, as protests against a proposed extradition bill spread across Hong Kong, Lennon Walls appeared throughout the territory: Sheung Shui, Sha Tin, Fanling, Causeway Bay, Kwun Tong, and more than 100 other locations according to a crowd-sourced map. Some appeared inside government buildings, including RTHK. They spread internationally too — Toronto, Vancouver, Tokyo, Berlin, London, Melbourne, Sydney, and Taipei all saw installations in solidarity. When Marco Leung Ling-kit, a democracy activist, died in June 2019, artists in Prague painted a memorial on the original Lennon Wall: his yellow raincoat, and the words "Hong Kong, Add oil."

Walls are usually built to stop things. This one was built to say them. The Hong Kong Lennon Wall worked because it asked for almost nothing from the people who contributed — just the willingness to write something down and leave it in a public place. That smallness was its power. Each note was easy to dismiss individually; tens of thousands of them in one place were not. The walls were vandalised, torn down, defended, and rebuilt. At the Yau Tong MTR station, on 10 July 2019, hundreds of people gathered after word spread that local residents — some suspected of being off-duty police officers — were threatening pro-democracy youth maintaining the wall. The conflict lasted several hours. Two retired police officers were among those arrested for assaulting democracy activists that night. A Post-it note had become something worth fighting over.