Gretzky's number, retired league-wide by the NHL in 2000. No player in the league may wear it.
What Edmonton had
Gretzky joined the Oilers in the WHA in 1978 and moved with them into the NHL. Between 1984 and 1988 Edmonton won four Stanley Cups.
He holds the records for career goals, assists and points, and the assists total alone exceeds any other player's points total.
9 August 1988
Peter Pocklington, the Oilers' owner, whose other businesses were under financial pressure, traded Gretzky, Marty McSorley and Mike Krushelnyski to the Los Angeles Kings.
Edmonton received Jimmy Carson, Martin Gelinas, first round picks in 1989, 1991 and 1993, and fifteen million US dollars.
The press conference
Gretzky broke down while reading his statement and was unable to finish it. The footage is among the most replayed in Canadian broadcasting.
His own later account is that he had told himself beforehand that he would not cry.
The political reaction
New Democratic Party MP Nelson Riis called in the House of Commons for the federal government to block the trade, describing Gretzky as a national symbol.
The government did not act. The demand was reported seriously at the time.
Pocklington was burned in effigy in Edmonton, and his comment that Gretzky had an ego the size of Manhattan made the reaction worse.
Los Angeles
The Kings had averaged well below capacity. Attendance rose immediately and the Forum sold out consistently.
California youth registrations increased sharply through the following decade.
The NHL added San Jose in 1991, Tampa Bay and Ottawa in 1992, Anaheim and Florida in 1993, and moved Winnipeg to Phoenix in 1996 and Quebec to Denver in 1995.
The sunbelt strategy that reshaped the league's economics is generally dated to this trade.
What it did not do
Gretzky reached the 1993 Stanley Cup final with Los Angeles and lost to Montreal. He never won another championship, and finished his career with St Louis and the New York Rangers, retiring in 1999.
Edmonton won the Cup in 1990 without him.
Why it goes on a wall
Because it is the clearest example of a single transaction changing the geography of a sport, and because the person at the centre of it was told about his own move and then had to explain it in public while unable to speak.
The day Canada lost him.