Comparisons have been made of the morphologic characters of 30-tree populations of Picea distributed from near the Arctic Circle in Alaska, to near the southern boundary of Arizona. Included are 7 populations of P. glauca beyond the geographic range of P. engelmannii, 12 populations of P. engelmannii beyond the geographic range of P. glauca, and 14 populations in the area of sympatry. Hybridization is evident in all populations in the area of sympatry, despite the appearance of many low-altitude trees as pure P. glauca and many high-altitude trees as pure P. engelmannii. The geographic range of P. glauca influence has been extended farther south than previously recognized—to eastern Washington and northern Wyoming. Distinguishing characters commonly given in taxonomic keys are less reliable than absolute measurements of the ovuliferous scales. The Holocene history of Picea is speculated upon.