Finding cost basis from stock before 2011

[MikeWTax]

Hi - 

I'm trying to find a good way to estimate the cost basis of a mutual fund which paid capital gains and dividends yearly. I have the cost basis after Jan of 2011. However, I have about 15 line items which likely were before that date with no cost basis and no purchase date.  I have been unable to get any further information from the holding investment bank. 

Any thoughts on ways I can estimate the cost basis so it is not zero?

[Anonymous_]

You can try BigCharts for historical data, but you sort of have to know the acquisition date(s).

https://bigcharts.marketwatch.com/historical

[RobertB4444]

You have to estimate when you bought them.  Once you have the best guess possible on that then the stock price for any stock in any year is available online and at the link @Anonymous_ posted.

@MikeWTax 

[MikeWTax]

Thanks, @RobertB4444 (and @Anonymous_). Yes, it's a bit difficult as I have so many N/A line items (likely 2 per year 1998-2010) but appreciate the input. I'll go with those steps (actually did just wanted to make sure my methodology was right. Thank you!