L. Jane Hastings was born and raised in Seattle, Washington. She received a Bachelor of Architecture from the University of Washington in 1952 and became licensed as an architect in the State of Washington in 1953 (she was the eighth woman to do so).

After working for a time in a firm, Hastings started her own practice in 1959. She formed the Hastings Group in 1974, eventually employing eight architects. The Hastings Group carried out work on more than 500 residential projects primarily in the Seattle and surrounding areas. Other projects of the Hastings Group include: small commercial and university facilities remodeling, Sea-Tac Airport renovations, I-90 bridge approach, and historic restoration of an Indian Tribal building.

Hastings' other professional activities include serving as a lecturer in Design Studios in the College of Architecture and Urban Planning at the University of Washington, and as an instructor in the Architectural Drafting Program at Seattle Community College for 10 years. She was also active in various professional organizations, including the American Institute of Architects (AIA) and the International Union of Women Architects (UIFA). She served as the president of the Seattle chapter of AIA in 1975, became a Fellow of AIA in 1980, and served as first woman chancellor of the College of Fellows in 1992.

During the course of her career, Hastings was the recipient of numerous awards and honors for her design work (including the AIA "Home of the Month" Annual Award in 1968), as well as for her other civic and professional activities. Her work was continually featured in the "Home of the Month" and Pictorial Sections of The Seattle Times, as well as in House Beautiful and House & Garden.

Hastings retired from full-time practice in the late 1990s.