Why was the presence of slave markets in washington, d.c. so controversial

First because Washington, D.C. was the capital city, and second because the slave trade was not seen as a good thing by the eyes of the foreign.

Explanation:

England was the first country in the world to free its slaves (in 1826), and then it began to compelled other countries to follow the example. But the United States did not make this until the 1860s, and slave trade was common in American cities. In Washington, D.C., however, as the capital city, it was something bigger. It was the center of the abolitionist campaign, but this was in contrast with the slave trade and slave markets.

The right answer is It led to the finalization of the border between the United States and British Canada.

On June 15, 1859, an American farmer named Lyman Cutlar shot and killed a Hudson’s Bay Company pig rooting in his San Juan Island potato patch. By so doing he nearly started a war between the United States and Great Britain. However, much more than a pig was involved. For more than 40 years, the two nations had been contending over the Oregon Country, which today comprises Washington, Oregon, Idaho, as well as portions of Montana and Wyoming and the province of British Columbia. On June 15, 1846, the two nations agreed upon the 49th parallel as the international boundary. The final sticking point was possession of the San Juan Islands, which was decided in favor of the USA in 1872.