What was probably the most difficult challenge facing construction the railroad in 1869

Concerns about the environment prompt congress to pass a $1 surcharge tax on each gallon of gasoline. which statement best describes the impact of such a tax

How did the mexcian war of independence differ from the american revolution?

What is the main difference between primary and secondary sources? a. primary sources are historical documents, and secondary sources are modern-day documents. b. primary sources are derived from museums and archives, and secondary sources are created by history students and academics. c. primary sources are found in ancient places with a rich history, and secondary sources are found in historical journals and blogs. d. primary sources are created during a particular historical era, and secondary sources are created by studying primary sources.