Calder is commissioned to make Lobster Trap and Fish Tail, a mobile he installs in the principal stairwell of the Museum of Modern Art's new building on West Fifty-third Street. (Lipman 1976, 332; Marter 1991, 197)

Calder is invited to make sculptures for an African Habitat being designed by Oscar Nitzschke for the Bronx Zoo. Calder conceives of treelike sculptures to be made in steel so they can withstand the abuse of the wild animals. Although the African Habitat is never realized, Calder creates four models for the project: Sphere Pierced by Cylinders, Four Leaves and Three Petals, Leaves and Tripod, and The Hairpins . (Canaday, "Lift")

30 April: Calder submits a Plexiglas stabile to a competition sponsored by Roehm and Haas at the Museum of Modern Art, New York. The work is exhibited at the Hall of Industrial Science during the New York World's Fair. (CF, exhibition file; Calder 1966, 175; Architectural Record 85 [June], 10)

9-27 May: "Calder Mobiles-Stabiles" is on view at the Pierre Matisse Gallery, New York. (CF, exhibition file)

25 May: The Calders' second daughter, Mary, is born. (Calder 1966, 174)

Summer: Sert and his wife, Moncha, pay an extended visit to the Calders in Roxbury. (Calder 1966, 174)

14 May-1 June: "Calder" is shown at the Pierre Matisse Gallery, New York. (CF, exhibition file)

Before 9 October: Marian Willard shows an array of Calder's jewelry to Valentina, a renowned haute couture dressmaker in New York. Valentina objects to the prices of the items and Willard takes them next to Harper's Bazaar where they are photographed. (CF, Willard to Calder, 9 October 1940)

11-14 October: A private exhibition of Calder's sculptures takes place inside and outside the home of Wallace K. Harrison and his wife, Ellen, in Huntington, Long Island. (MoMA, invitation; CF, Myra Martin to Ellen Harrison, 24 October 1940)

16 October: Carmel Snow, the legendary editor of Harper's Bazaar writes to Marian Willard: ... the photographs of Sandy Calder's jewelry turned out beautifully .... we will publish these either in December or January.... (CF, Snow to Willard, 16 October 1940)