1863: John D. Rockefeller partners with Maurice B. Clark and Samuel
Andrews to open his first oil refinery.
1871: J. P. Morgan becomes a partner in the banking firm Drexel, Morgan &
Co.
1875: Andrew Carnegie uses money from earlier investments to open his first
steel mill.
1882: Rockefeller forms the Standard Oil Trust, which controls most U.S. oil
production.
1889: Morgan merges several electricity companies to found General Electric.
1892: Striking workers at Carnegie's mill in Homestead, Pennsylvania, clash
with hired security forces.
1895: Morgan takes over Drexel and restructures it to become J. P. Morgan &
Co.
1899: Carnegie combines several steel mills that he has purchased into
Carnegie Steel.
1901: Morgan buys out Carnegie for $480 million and forms U.S. Steel.
1914: The United Mine Workers strike at a Rockefeller-owned coal mine in
Ludlow, Colorado, ends in a massacre.

The information in the timeline most directly relates to the development of
which movement?

A. Temperance reformers
B. Farmers' cooperatives
C. Settlement houses
D. Labor unions