What part of the USA and why is there a high population density?

Due to the fact that since the beginning of the 19th century, there have been a concentration of immigrants from European countries on the East Coast and North-East of the United States, the largest agglomerations of the country’s population have been formed in this territory. Due to the presence of a large number of minerals, fresh water and other resources, at the moment the average population density of this territory reaches 100-150 people per square kilometer, taking into account the fact that the total US density is 35 people per km2.