Complex sentence: The current boundaries of Elmont were decided upon in 1898; at this point, Nassau County was erected, leading to conflict over land, and monies owed as a result of Elmont's boundary shift from Queens.
Split into simpler sentences: The current boundaries of Elmont were decided upon in 1898, when Nassau County was established. This led to conflict over land, and monies owed as a result of Elmont's boundary shift from Queens.