What are two issues that made it difficult for explorers during the columbus's
time to explore unknown territory by sea?

regarding the law, the 15th amendment was specifically designed thinking in the rights of black free men.

even though ratified on february 3, 1870, the promise of the 15th amendment would not be fully applied for a long time.poll taxes and literacy tests would allow southern states disenfranchise african americans. only in 1965 the voting rights for african americans would be actually able to vote in the south.

in 1965, president johnson signed the voting rights act, which aimed to overcome legal barriers that prevented african americans from voting as it was guaranteed by the 15th amendment to the u.s. constitution.

the progressive era is a period of widespread social activism and political reform across the united states that spanned from the 1890s to the 1920s.[1] the main objectives of the progressive movement were eliminating problems caused by industrialization, urbanization, immigration, and political corruption.

the movement primarily targeted political machines and their bosses. by taking down these corrupt representatives in office, a further means of direct democracy would be established. they also sought regulation of monopolies (trust busting) and corporations through antitrust laws, which were seen as a way to promote equal competition for the advantage of legitimate competitors.

many progressives supported prohibition of alcoholic beverages, ostensibly to destroy the political power of local bosses based in saloons, but others out of a religious motivation. at the same time, women's suffrage was promoted to bring a "purer" female vote into the arena.a third theme was building an efficiency movement in every sector that could identify old ways that needed modernizing, and bring to bear scientific, medical and engineering solutions; a key part of the efficiency movement was scientific management, or "taylorism".

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hi the answer to your question is

to control offices

this sparked alotof controversy more over ending the articles of federation