This expansion more or less follows the Mississippi River. The species prefers wooded city parks and woodlots. A quick look at eBird illustrates their range and various extralimital sightings. Birds have been sighted around the northern midwest, and as far afield as British Columbia, Oregon, and the East Coast. Ornithologist do not know if these distant sightings are of escaped cage birds, sparrows arriving by ship from Europe or Asia, or individuals originating from their expected range in North America.
The source for most of the information and the quote in this post is Barlow and Leckie (2000). Not included in their account in The Birds of North America is a specimen from Huron, South Dakota, of an Eurasian Tree Sparrow collected on 19 April 2005 by a Purple Martin enthusiast clearing his bird houses of House Sparrows.