The word panorama has a number of definitions, but here it means “an unobstructed or complete view of an area in every direction.” What did sweeping visions of America’s natural treasures and great cities mean to viewers? And how were these paintings and photographs—Romantic, often Transcendentalist—exploited to inspire nationalism and even imperial expansion? The New-York Historical Society looks at panoramas from the 17th to 21st centuries. —L.J.