Today, with 97 percent of the archipelago off limits for colonization, man's modern intrusion is tourism.
Only 20 of them are considered non-contributing, most of them modern commercial intrusions like supermarkets and gas stations.
Only one is a modern intrusion.
Many of the district's 240 buildings date to the 19th century, with a few 18th-century structures and modern intrusions.
Similar projects targeted the blocks west of North Swan, leaving gaps and modern intrusions that also persist today.
The Colonial Parkway was planned and is maintained to reduce modern intrusions.
As of 1986, the district's area included only three modern intrusions.
Although there are a number of modern intrusions along Springfield's main commercial arteries, these have not proved so numerous as to be overwhelming.
It will also be devoid of almost any modern intrusions.
Avert your eyes from such modern intrusions as the new Bank of Austria building and you are transported back a century.