The maps below are on the National Library of Scotland web site, https://maps.nls.uk/, which is well worth exploring
MARIO (Maps & Related Information Online), is another site worth exploring at https://mario-lancashirecounty.hub.arcgis.com/
1840's map of the farmland that became the park, along with a modern LiDAR image showing the faint remnants of field boundaries and the path. Note that the railway line was built around 1840 and cuts through old field boundaries. The field boundaries are visible on the modern LiDAR images and can sometimes be seen on the ground
1840's map showing where the bridge was, along with Google satellite view of the park recently
MARIO has an 1890's map where 'Ingol Ashes' has become 'Bostock's Farm', for the most part. Select 'Aerial Photography and Historic Maps' on the 'Map Layer' to find. Unfortunately links to the maps don't seem to work.
1914 map showing the park but none of the built features like the pavilions or gatehouse
(1948 aerial photo of the park showing extensive allotments both to the south of the current ones and to the west - unfortunately Historic England have had to suspend this service)
1958 map showing allotments bridge in its current position, extended allotment site, swimming pool and aviary
MARIO has a 1960s aerial photo showing the allotments going across to the path (see above)
1968 map, Bostocks farm has now gone and the allotments back to their original size
For more historic images of the park, see Preston Digital Archive