Also note the tall, stately (elms or maples?) which resided along the sidewalk. You will see darkened bands around eye-level of these trees. They were tar or wax insect traps to keep leaf and tree-killing worms from gaining advance up these trees. These critters eat into all of the leaves, killing the tree in many instances. This problem arises here in New England every two decades or so and it has been the death knell to many beautiful, century-plus-year old trees. The buggy invaders typically cannot make it above the tar boundaries as you see. This basic idea still is used today and with environmental-friendly chemicals.