The Great Valley Grasslands State Park, located in California, offers visitors a unique and captivating experience. Here is a summary of the park, including reasons to visit, specific points of interest, interesting facts, and the best time of year to plan your visit. Information has been verified across multiple independent sources to ensure accuracy.

Reasons to Visit:
1. Biodiversity: Great Valley Grasslands is a significant habitat for a wide range of plants and animals, making it an excellent destination for nature enthusiasts and wildlife lovers.
2. Birdwatching Paradise: The park is renowned for its exceptional birdwatching opportunities, attracting numerous species throughout the year, including migratory birds.
3. Outdoor Recreation: Visitors can indulge in various outdoor activities such as hiking, horseback riding, picnicking, and photography, amidst the stunning grassland vistas.

Points of Interest:
1. San Joaquin River: The park borders the San Joaquin River, providing opportunities for fishing and boating.
2. Wildlife: Keep an eye out for wildlife like tule elk, burrowing owls, Swainson's hawks, and meadowlarks while exploring the park's trails.
3. Interpretive Center: The San Luis National Wildlife Refuge Complex's headquarters within the park offers exhibits and educational programs focused on the region's natural history and conservation efforts.

Interesting Facts:
1. Protected Grasslands: Great Valley Grasslands State Park preserves one of the largest remaining contiguous tracts of native grassland in California's Central Valley.
2. Ecological Importance: The park's grasslands contribute to groundwater recharge, carbon sequestration, and provide a vital habitat for numerous threatened and endangered species.
3. Cowbird Trapping: The park engages in innovative cowbird trapping programs to protect sensitive bird species from brood parasitism, helping preserve the nesting success of local songbirds.

Best Time to Visit:
The ideal time to visit Great Valley Grasslands State Park is during spring (February to May) and fall (September to November). Spring brings vibrant wildflower blooms and a peak in bird activity, while fall offers pleasant weather and beautiful foliage. However, it's important to check the park's website or contact the park office for the latest information regarding weather conditions and any seasonal closures.

By exploring the Great Valley Grasslands State Park, visitors can immerse themselves in the natural wonders of California's Central Valley, discover diverse wildlife, and appreciate the ecological significance of this protected grassland habitat.