Previously I recommended historical GIS resources include:
- AllHistory (Perfect World's feature-rich platform with polished UI)
- Taiwan-maintained Chinese Historical WMTS Service (China-exclusive basemaps)
Recently discovered OldMapsOnline - a globally-oriented historical mapping solution.
Overview
Free open-access platform aggregating 500,000+ high-res historical maps (16th-21st c.) from institutions including:
• British Library
• Harvard Library
• David Rumsey Map Collection
Volunteer-powered expansion supports researchers/educators.
Official site: https://www.oldmapsonline.org/
Operational differences from AllHistory yield distinct features.
Core Asset: Historical Map Repository
• Global coverage from elite archives
• Region-specific discovery (e.g. Shandong Province):
• Georeferenced maps support overlay analysis
Global Timeline
Synchronized visualization of dynasties/rulers/events worldwide: 
Historical Entities
• Figures/events sourced directly from Wikipedia
• Less curated than AllHistory's structured data:
Mainland users: Access may require workarounds
Platform Comparison
| Feature | OldMapsOnline | AllHistory |
|---|---|---|
| Map Archive | ★★★★★ (Core strength) | ★★★☆☆ |
| Timeline Function | ★★★★☆ (Global synchronization) | ★★★★☆ |
| Data Quality | ★★☆☆☆ (Raw Wikipedia feeds) | ★★★★☆ (Curated datasets) |
| Operations | Community-driven | Corporate-managed |
Critical Note: Inaccurate PRC post-1949 borders - persistent issue in foreign platforms.
Contribute your historical GIS resources below!