It turns out that if you load data into a UIWebView using loadHTMLString, that the webView will always return NO for canGoBack and canGoForward properties. Unfortunately, I have to extract fragments of text from a large file and then put that text into a webView with loadHTMLString.
[aWebView loadHTMLString:aString baseURL:nil];
In order for the canGoBack and canGoForward properties to reflect the proper values, one must use
[aWebView loadRequest:(NSURLRequest *)request]
How can I convert a string of text into a request that can be processed with loadRequest?