The first time I encountered this tree was in east Vancouver, near Grandview elementary school. I was amazed at how closely it resembled orange blossom, though it has nothing to do with orange. It looks as if it belongs to the fabacea (or legumes) family, just like Spanish Broom, mimosa and Sweet Pea.
P.s. Thanks to my reader, Veronica, I now know the identity of the mystery tree: Robinia pseuodoacacia, aka Black Locust or Witte Acacia. Veronica, please email me so I can thank you properly with a mini of my mimosa perfume, Les Nuages de Joie Jaune.
According to W.A. Poucher's Perfumes, Cosmetics and Soaps (Vol. 1, p. 296): "Source: Natural. Flowers of Robinio pseudo-acacia, L. Leguminosae. The absolute is obtained by extraction with volatile solvents. Possesses an intense odour of the blossoms. Chemical: Contains indole, methyl antrhanilate, linalool, benzyl alcohol, heliotropin, and trepineol, with traces of aldehydes and ketones of peach odour".