Bigleaf magnolia is the largest-leaved and largest-flowered magnolia species in the world. It also has the largest simple leaves of any tree in North America.
Native to the southeastern USA, its habitat is “alluvial woods and sheltered valleys, piedmont“. It is listed as a species of global least concern by the IUCN Red List, although its conservation status may be different locally. For example, the Flora of North America entry (first link in this paragraph) states it is apparently extirpated in Arkansas (no longer present, i.e., extinct in that area).
The species has been in cultivation since 1800. It is recommended as a specimen tree in park or large landscapes, with a near-requirement that it be grown in a sheltered spot to prevent the wind from tattering its leaves (but here’s a suggestion to the contrary). The plant featured in today’s photographs is sheltered by other trees in UBC’s Carolinian Forest Garden (see this forum thread).