1. In 1804, the first steam engine railway run was established in New Jersey, connecting Hoboken to Jersey City for the first time. This revolutionized transportation in the state and paved the way for further expansion.

2. On May 15, 1911, the United States Supreme Court issued a decision in Standard Oil Co. of New Jersey v. United States, ruling that Standard Oil was guilty of violating the Sherman Antitrust Act. This decision marked the beginning of the breakup of the company into smaller, competing entities.

3. The first world-renowned boardwalk was opened on May 15, 1870, in Atlantic City, New Jersey. This was one of the earliest and most significant milestones in the development of this now-famous resort town.

4. On May 15, 1938, the groundbreaking ceremony was held for the construction of the Lincoln Tunnel, connecting New Jersey and New York City. The creation of the tunnel vastly improved transportation and commerce between the two states.

5. May 15, 1975, was a historic day in New Jersey as the state officially designated the tomato as the official state vegetable. While many consider the tomato a fruit, New Jersey Legislature declared it a vegetable, recognizing the importance of its cultivation to the state's economy.